What does it mean when antibodies in blood?

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What is antibodies?

antibodies in blood
antibodies in blood

Antibodies in blood or interstitial fluid refer to the immunoglobulin that is produced by the plasma cells differentiated from B lymphocytes under the stimulation of antigen by the body's immune system and can specifically bind to the corresponding antigen.

The main function of antibody is to combine with antigen (including foreign and self), thereby effectively removing foreign bodies such as microorganisms and parasites that invade the body, neutralizing the toxins released by them or removing certain self-antigens, so that the body can maintain balance. But sometimes it can cause pathological damage to the body, such as anti-nuclear antibodies, anti-double-stranded DNA antibodies, and anti-thyroglobulin antibodies.

What does it mean when antibodies in blood?

When pathogens or other foreign proteins enter the human body, the human body will produce corresponding antibodies to fight against the corresponding anti-antibodies. Some antibodies are salubrious, and other antibodies are harmful.

Having antibodies in the body means that the body's immune system has been exposed to a certain antigen, so that certain antibodies can be detected in the blood circulation. Some antibodies may not mainly exist in the blood circulation but in the mucosa. The body's antibodies are the main component of humoral immunity produced by the body's immune system. It is exposed to the corresponding antigen. After a virus or bacteria infect the human body, it may produce a variety of antigens. These antigens can make the body immune system recognize and produce corresponding antibodies. Some antibodies have a protective effect, namely protective antibodies. For example, hepatitis B surface antibodies can be produced after hepatitis B vaccine injection. This is a protective antibody. After being produced, people will no longer get hepatitis B.

But some antibodies in blood are not protective antibodies. For example, after getting hepatitis C, the body’s immune system will detect hepatitis C antibodies, but this antibody is not a protective antibody. It can only indicate that a person is likely to be infected with hepatitis C. If it is an antibody test for AIDS, it also means that the person is infected with HIV, because it is not a protective antibody.

And it depends on the specific antibody to determine whether there is any disease. Generally, there will be an antibody blood test, and if the corresponding antigen is negative, meaning there was an infection.

What does it mean when you have too many antibodies in your blood?

The high level of antibodies in blood may be due to multiple infusions of plasma, which contains more antibodies. If bone marrow and kidney transplantation are performed at this time, it may cause more serious rejection.

Some patients with hyperthyroidism are often accompanied by significantly elevated thyroid autoantibody TPOAb, and TGAb. This may be hyperthyroidism caused by autoimmune thyroiditis. Autoimmune diseases that will lead to increased thyroid autoantibodies cause long-term diffuse destruction of thyroid tissue. At this time, if the patient completes the thyroid color doppler ultrasound, heterogeneous or grid-like thyroid gland can be noticed.

Generally speaking, antibodies in the blood will not disappear automatically. Antibodies are produced by B lymphocytes in the blood, and B lymphocytes are produced by lymphoid organs, and they are in a constant balance between production and death. Even if you donate blood, it will not affect this balance.

High antibodies in the blood is a general and vague term. It is recommended to go to the hospital to ask the doctor for specific information about antibodies and underlying diseases.

Antibodies in blood types

Antibodies are immunoglobulins, but not all immunoglobulins are antibodies. As long as the glycoprotein has an antibody structure, it is an immunoglobulin. Immunoglobulins are expressed as Ig. It has been found that humans have five types of immunoglobulins, namely IgG, IgM, IgA, IgD and IgE.

immunoglobulin structure
immunoglobulin structure

There are only three types of immunoglobulins related to blood group, namely IgG, IgM and IgA. There are so-called "natural antibodies" and "immune antibodies" according to whether there is detectable antigen stimulation when antibodies appear in the body.

Antibodies that appear in the body's serum without antigen stimulation are called "natural antibodies"; the antibodies produced in the serum after the body is stimulated by the same or heterogeneous antigens are called immune antibodies. There are two explanations for the production of "natural antibodies": one is that there are "antigen-sensitized" cells in the body that can produce specific antibodies without antigen stimulation; the other is that "natural antibodies" are heteroagglutinins. There are some substances similar to blood type antigens in the surrounding environment. After the body contacts these substances, cross-reactive antibodies are produced. For example, some bacteria contain antigens similar to A and B antigens. When people inhale or swallow these bacteria, cross-reactive antibodies are produced.

"Natural antibodies" react actively with their corresponding antigen cells at low temperatures. Many "natural antibodies" are inactive when the temperature exceeds 25°C. Some "natural antibodies" have the ability to bind complement, while others do not. For example, most of Lewis blood group antibodies have the ability to bind complement, while anti-M and anti-N do not. "Native antibodies" are usually IgM immunoglobulins, but some "natural antibodies" are IgG immunoglobulins, such as anti-Lea, anti-M, anti-N, and anti-K "natural antibodies" are IgG.

Immune antibodies are antibodies produced by the body in a hyperimmune state after being stimulated by the same or heterogeneous antigen. Blood transfusion and pregnancy are the main reasons for the production of alloimmune antibodies. People who have received vaccines, antiserum (diphtheria, tetanus antitoxin) injections, and those who have used pig stomach and liver extracts have increased anti-A and anti-B titers in their serum. This is a case of immune antibodies caused by heterologous immunity example.

Immune anti-A and anti-B are different from "natural antibodies" in many ways. Some antibodies and their corresponding antigen cells can agglutinate in saline medium. Such antibodies are called complete antibodies; some antibodies can only bind to (sensitize) their corresponding antigen cells in saline medium, but they cannot agglutinate. Such antibodies are called incomplete antibodies. To make incomplete antibodies and their corresponding antigen cells agglutinate, other media must be used, such as enzyme treatment of red blood cells, or suspension of red blood cells in a macromolecular colloidal fluid, or the help of antiglobulin serum. In fact, complete antibodies generally refer to IgM antibodies, while incomplete antibodies are mostly IgG antibodies. IgA is mainly in the secretion fluid and does not occupy a major position in blood types of antibodies.

Antibodies in blood during pregnancy

Items that should be checked before pregnancy are, hepatitis A, hepatitis B five items, hepatitis C, hepatitis D, hepatitis E, syphilis, AIDS, chlamydia, mycoplasma, gonococcus rapid test, lincoccus tablets, liver function set, prenatal RH check, gynecology + leucorrhea routine examination, vaginal B ultrasound, chromosome examination, semen routine examination, blood routine examination, urine routine examination, and blood clotting.

If you have Rh-negative blood and you are pregnant for the first time, you don’t need to be too nervous. Do a blood immunological prenatal test (blood group antibody test) from the 5th month of pregnancy, and then do an antibody test in the 7th and 9th months of pregnancy, and do the test again about half a year after delivery.

The first baby rarely produces antibodies during pregnancy. Anti-D imunoglobin can be injected within 72 hours after delivery. If anti-D immunoglobulin has been injected at 26-28 weeks of pregnancy, it will achieve a better effect if you receive another injection after delivery.

Anti-D immunoglobulin is to prevent the production of anti-D antibodies. It is to protect your own reproductive rights and the right of blood donation and blood transfusion. Therefore, it is not advisable to wait until antibodies are produced. Once the anti-D antibody is produced, it is difficult to eliminate it, so prevention obviates the anxiety.

Antibodies in blood may also cause infertility, such as immune infertility. Immune infertility is infertility caused by immune factors, such as anti-sperm antibodies, anti-endometrial antibodies, anti-egg antibodies and other factors. If you have specific needs, then go to a regular hospital for further examination.

Conclusion

There are so many types of antibodies in blood that you cannot simply define good or bad. It is recommended to go to the hospital for a full-body examination regularly, and only then the diseases discovered in time can be treated in time.

Want to learn more about antigens and antibodies? Read about FC stand information and monoclonal and polyclonal antibodies.

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Humanized antibody vs human antibody

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What is humanized antibody?

Humanized antibody mainly refers to the re-expressed mouse monoclonal antibodies modified by gene cloning and DNA recombination technology. Most of its amino acid sequence is replaced by human sequence, which basically retains the affinity and specificity of the parent mouse monoclonal antibodies, and reduces heterogeneity at the same time. Its application would be beneficial to the human body.

humanized antibody
humanized antibody

Humanized antibody means that the constant region of the antibody (CH and CL regions) or all of the antibody is encoded by human antibody genes. And humanized antibodies can greatly reduce the immune side effects caused by heterologous antibodies to the human body.

Classification of humanized antibodies

According to different principles of action, humanized antibodies can be divided into four categories: human-mouse chimeric antibody, modified antibodies, resurfaced antibodies and human antibodies.

1. Human-mouse chimeric antibody

What is a chimeric antibody? Human-mouse chimeric antibody, that is, the crossable region of the antibody is derived from small rat McAb, while the constant region is derived from human antibody. Such antibodies not only maintain the specificity and affinity of the original McAb, but also greatly reduce the immunogenicity in the human body.

Chimeric antibody inserts the light and heavy chain variable region genes of the heterologous monoclonal antibodies into an expression vector containing the constant region of a human antibody, transforming mammalian cells to express the chimeric antibody by DNA recombination technology. The V regions of the light and heavy chains are heterologous, while the C region is of human origin, so that nearly 2/3 of the entire antibody molecule is of human origin. The antibody produced in this way reduces the immunogenicity of the heterologous antibody while retaining the ability of the parent antibody to specifically bind to the antigen.

2. Modified antibodies

Modified antibody is also called CDR grafting antibody. The CDR of the variable region in the antibody is the region where the antibody recognizes and binds to the antigen, which directly determines the specificity of the antibody. The CDR of the mouse monoclonal antibodies is transplanted to the variable region of the human antibody to replace the CDR of the human antibody, so that the human antibody obtains the antigen binding specificity of the mouse monoclonal antibody while reducing its heterogeneity. However, although the antigen is mainly in contact with the CDR of the antibody, the FR region often affects the spatial configuration of the CDR.

Therefore, after replacing the human-derived FR region, the V region where the mouse-derived CDR and the human-derived FR are embedded may change the CDR configuration of the single antigen, and the ability to bind the antigen will decrease or sharply decrease. Although it has been possible to carry out molecular design of antibodies and introduce certain key residues of mouse FR regions into human FR regions, if properly configured, their affinity can be equivalent to that of the original mouse antibody, but humanized antibody often fails to reach the affinity of the original mouse monoclonal antibody.

3. Resurface antibodies

Surface remodeling antibody refers to the humanized modification of amino acid residues on the surface of heterologous antibody. The principle of this method is to replace only the regions that are significantly different from the SAR of human antibodies.

On the basis of maintaining antibody activity and reducing heterogeneity, amino acid substitutions similar to the surface residues of human antibodies should be selected; in addition, the replaced segments should not be excessive. And try not to replace residues that affect the size, charge, hydrophobicity of the side chain, or may form hydrogen bonds to affect the conformation of the antibody complementarity determining region (CDR).

4. Human antibody

Human antibody refers to the transfer of human antibody genes through transgene or transchromosome technology to transfer all the human antibody-encoding genes to genetically engineered animals with antibody gene deletions, so that the animals can express human antibodies to achieve human antibodies purpose.

5. Humanized antibody vs human antibody

According to the different sources of monoclonal antibodies, they can be divided into mouse antibodies, chimeric antibody, humanized antibodies and human antibodies. The so-called human monoclonal antibody means that 100% of the gene source is from human. However, in fact, human monoclonal antibodies are also produced in mice.

humanized antibody vs human antibody
humanized antibody vs human antibody

By transferring human genes related to antibody production to mice, the structure of antibodies in mice can be the same as those of human antibodies. Therefore, human antibodies ≠ antibodies made directly from human cells, but the structure of the antibody is 100% encoded according to human genes. Humanized monoclonal antibodies are mostly human-derived and are fused with mouse-derived components. In recent years, scientists have deliberately kept the key beneficial gene structure of mouse resistance in the human frame through genetic engineering, which plays a special role, just like optimizing reprocessing.

For example, Ichizumab (humanized monoclonal antibody) retains 1.8% of the mouse-derived ingredients, which integrates advantageous genes, so it achieves high affinity and rapid onset of action.

The development of antibody humanization

1. Antibody Humanization

Humanization of antibodies is an important part of experimental research on the production and preparation of recombinant antibodies (monoclonal antibodies). The antibody humanization is the process of developing from mouse antibody to human antibody.

More than a hundred years ago, the discovery of the principles of antibody-antigen specific binding and the passive immune characteristics of antibodies opened up a new way of disease diagnosis. The advent of monoclonal antibody technology in 1975 accelerated the widespread application of this method. In the initial stage, most of the monoclonal antibodies used clinically were mouse monoclonal antibodies. Due to the species specificity of humans and mice, there are various restrictions on the use of them.

Although the mouse antibody is specific to the target antigen and can specifically bind to the target antigen, it cannot activate the corresponding human effector system, such as antibody-dependent cell-mediated cytotoxicity (ADCC), complement-dependent cytotoxicity (CDC), etc., so that the antigen-antibody reaction cannot occur normally.

In addition, the mouse antibody enters the human body as a foreign protein, which will cause the human immune system to respond and produce specific antibodies taking the mouse antibody as the antigen, that is, the human anti-mouse antibody. Usually heterologous protein with a short half-life will be quickly eliminated in the human body. Due to various limitations in the clinical application of mouse antibodies, people use recombinant DNA technology to humanize mouse antibodies to humanize antibodies.

2. Principle

The humanization of mouse antibody is to make it have a very similar profile to the antibody molecule in the human body through genetic modification, thereby evading recognition by the human immune system and avoiding the induction of HAMA response. The humanization of antibodies should follow two basic principles, that is, to maintain or improve the affinity and specificity of the antibody: greatly reduce or substantially eliminate the immunogenicity of the antibody.

The process of antibody humanization has gone through three stages: human-mouse chimeric antibody, humanized antibody and human antibody. According to different principles of action, humanized antibodies can be divided into four types: human-mouse chimeric antibody, modified antibodies, resurfaced antibodies, and human antibodies.

3. Mouse antibody VS humanized antibody

Mouse antibodyHumanized antibodyHuman antibody
Antibody TypesRecombinant antibodyRecombinant antibodyRecombinant antibody
StructureBoth variable and constant regions are derived from mouse antibodiesThe variable region is from small (large) mouse McAb, and the constant region is from a human antibodyBoth variable and constant regions are derived from human antibodies
ImmunogenicityStrongStrongStrong
Stimulate the human immune responseEasily cause human immune response and produce HAMAWeakWeak
Clinical applicationLarge restriction, small application rangeWideWide
Difficulty of preparationEasyDifficultDifficult

4. Application

In recent years, the emergence of humanized antibody and human antibodies has brought new hopes for clinical applications. They show excellent effect in the treatment of tumors, autoimmune diseases and cardiovascular diseases, as well as anti-transplant rejection and anti-viral infections. They can reduce the adverse reactions of traditional tumor drug therapy, protect the function of transplanted organs, and be the induction of solid organ transplantation therapy.

The US FDA approved the first human-mouse chimeric Fab antibody (ReoPro) in 1994. This drug has been widely used in the treatment of various cardiovascular diseases, mainly used to prevent restenosis after coronary artery formation. Research in recent years shows that humanized antibodies are prospecting in anti-viral infection (such as HBV, HCV, HIV and other viral infectious diseases).

Conclusion

Human antibody belongs to humanized antibody. Humanized antibody means that the constant region of the antibody (CH and CL regions) or all of the antibody is encoded by human antibody genes. While human antibodies mean that all antibodies are encoded by human antibody genes, allowing animals to express human antibodies.

Want to learn more about antigens and antibodies? Read about FC stand information.

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The relationship between immunoglobulin and diseases

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immunoglobulin-and-diseases

What is immunoglobulin?

Immunoglobulin (Ig) refers to a globulin that has antibody (Ab) activity or chemical structure and is similar to antibody molecules. Immunoglobulin is a tetrapeptide chain structure composed of two identical light chains and two identical heavy chains connected by interchain disulfide bonds.

What are the 5 immunoglobulins? Immunoglobulins are divided into five categories, namely immunoglobulin G (IgG), immunoglobulin A (IgA), immunoglobulin M (IgM), immunoglobulin D (IgD) and immunoglobulin E (IgE).

The immune system is composed of immune tissues, organs, immune cells and immune active molecules. Immunoglobulin is a class of immunologically active molecules which include immune cell membrane molecules, such as antigen recognition receptors, differentiation antigens, major histocompatibility molecules, and some other receptor molecules. It also includes molecules synthesized and secreted by immune and non-immune cells, such as immunoglobulin molecules, complement molecules, and cytokines. Immunoglobulin is a concept in chemical structure. The chemical basis of all antibodies is immunoglobulin, but not all immunoglobulins have antibody activity.

Immunoglobulin Structure

Immunoglobulins can be divided into antibodies and membrane immunoglobulins. Antibodies are mainly found in serum, but also in other body fluids and exocrine fluids. Their main function is to specifically bind antigen.

Membrane immunoglobulin is an antigen receptor on the membrane of B cells, which can specifically recognize antigen molecules. In the body, antibodies and antigens can directly exert effects after binding. For example, antitoxins can neutralize exotoxins, virus-neutralizing antibodies can prevent viruses from infecting target cells, and secreted IgA can inhibit bacterial adhesion to host cells.

In vitro, agglutination and precipitation may occur after the antibody binds to the antigen. Immunoglobulin can activate complement, binding to the Fc receptor on the cell surface, (Fc is a crystalline fragment. Hydrolyze IgG molecules with papain can obtain two Fab and one Fc fragment. This fragment can interact with effector molecules and effector cells, but can’t bind to antigens.) so exhibiting different biological effects, such as opsonization, antibody-dependent cell-mediated cytotoxicity, and mediating type I hypersensitivity.

Through the placenta and mucosa, IgG is the only type of Ig that can pass through humans’ placenta. The transfer of maternal IgG to the fetus through the placenta is an important natural passive immunity, which is of great significance for neonatal anti-infection. Secreted IgA can pass through the mucosa of the digestive tract and respiratory tract, which is the main factor of the body's mucosal local immunity. In addition, antibodies have positive and negative regulatory effects on the immune response.

Immunoglobulin and diseases

1. Immunoglobulin and diabetes

China is now facing a whole new problem: the largest diabetes epidemic in the world. According to a recent study, one in ten adults in China has diabetes, and another 16% are on the verge of developing diabetes. According to the latest findings, the incidence of diabetes in China is almost close to 11% in the United States, surpassing most western countries such as Germany and Canada.

At present, many research data on the epidemiology, pathology, serology of diabetes shows that the onset of diabetes is closely related to autoimmunity, especially insulin dependence. Because the molecular structure of some substances (antigens) on the insulin-secreting B cells in the pancreatic islets is similar to the viral antigens, when the self-immunity is low, the autoantibodies will mistake it for an "invader", thus generating immunity against its own islet cells reaction. They attack on B cells and cause "fights between their own people". As a result, almost all pancreatic islet B cells are "dead", and the function of secreting insulin is severely reduced or even failed. Once the body lacks this blood sugar lowering hormone, there will be a series of manifestations of high blood sugar.

Infusion of intravenous C can help reduce the immune system's attack on insulin, help the recovery of insulin cells, and make insulin secrete normally.

2. Immunoglobulin and cancer

Normal human immunity has the effect of resisting cancer, because cancer cells are very different from normal human cells and belong to "heterogeneous substances." Specifically, immunity against cancer means that the body uses immune cells or immunologically active substances (such as antibodies) to recognize mutations or cancerous cells in the body in time, and then eliminate them. This effect is also called "immune surveillance", which is equivalent to the human body's warning system against cancer. Therefore, when the body is invaded by cancer cells, its onset depends on the body's immunity.

3. Immunoglobulin and rheumatic diseases

According to statistics from the World Health Organization, the incidence of rheumatism in the world’s population of nearly 6 billion is as high as 5%. Nearly 300 million people suffer from rheumatoid arthritis and other rheumatoid diseases. Patients often have kidneys, heart, lungs, liver, blood and immune system diseases and functional abnormalities, which is most common in the elderly.

As the main synthetic product of the immune system, immunoglobulin has obvious anti-disease effects. It can regulate the normal operation of the human immune system, stabilize the human immune defense line, resist the invasion of bacteria and viruses in vitro, and prevent fever, fatigue and joints inflammation caused by susceptible factors. So middle-aged and elderly people can enjoy their old age in peace.

Where does immunoglobulin come from?

1. Where does immunoglobulin come from?

IgG is the only immunoglobulin that can be passed to the fetus through the placenta, and breast milk is rich in immunoglobulins. After the baby is born, the immune factors transferred by the mother's placenta and the mother's milk during the lactation period enable the baby to get the initial disease resistance.

2. Synthesis of immune organs in the body

Most of the immunoglobulin required by the human body depends on the synthesis of immune organs. As children grow up to about 15 years old, their immune organs gradually mature and basically reach the level of adults. By the age of 22, the immune organs have the strongest function and the strongest ability to synthesize immune globulin. Later, with the increase of age, the immune organs began to shrink. After the age of 55, some immune organs even completely degenerate, the number of synthetic immunoglobulins decreases, and the immune globulin in the body will sharply decrease.

3. In vitro supplementation

In vitro injection of gamma globulin is a relatively quick and effective way to enhance the body's resistance to prevent infection. It is mainly used for the prevention and treatment of immunodeficiency diseases, infectious hepatitis, measles, chickenpox, mumps, herpes zoster and other viral and bacterial infections. It can also be used for endogenous allergic diseases such as allergic rhinitis, eczema, myasthenia gravis, ITP, systemic erythema lupus and Kawasaki disease.

Significance of immunoglobulin test

Immunoglobulin is a type of protein with antibody activity in human serum and body fluids, also known as gamma globulin. It has antibacterial and antiviral effects, strengthens the phagocytosis of cells, and can kill or dissolve pathogenic microorganisms under the cooperation of complement. It is an important component against diseases.

immunoglobulin structure
immunoglobulin structure

Serum immunoglobulins can be divided into five types, namely IgG, IgM, IgA, IgD, and IgE. The normal value varies due to different subjects, ages, regions, and methods. Various immunoglobulins not only differ in quantity, but also have their own characteristics in function:

1. IgG

Most antibodies with antibacterial, antiviral, and antitoxin effects belong to IgG. It is the only immunoglobulin that can pass through the placenta. Increased IgG is seen in IgG multiple myeloma, systemic lupus erythematosus, rheumatoid arthritis, chronic active hepatitis, tuberculosis, kala-azar and certain infectious diseases. Decrease is seen in nephrotic syndrome, certain tumors, leukemia, heavy chain disease, light chain disease and certain immunodeficiency diseases.

2. IgA

IgA has antibacterial and antiviral effects. It cannot pass through the placenta, and children can only get it from breast milk.  

Reference value: 0.7~3.9 g/L for adults.

There are two types of IgA in human blood, namely serotype and secretory type. The former exists in the form of a monomer, and the latter is composed of a connected dimer and secretory sheet. The place where synthesis and secretion take place are located in the intestine, respiratory tract, breast, salivary glands and lacrimal glands, so they mainly exist in the gastrointestinal tract, bronchial secretions, colostrum, saliva and tears. They are the main antibodies involved in mucosal immunity and play an important role in local anti-infection. It is through colostrum that babies obtain secretory IgA, which achieves the effect of natural passive immunity. 

Elevated IgA is seen in IgA type multiple myelopathy, systemic lupus erythematosus, rheumatoid arthritis, liver cirrhosis, eczema, thrombocytopenia and other diseases. The low iga levels is seen in heavy chain disease, light chain disease, malabsorption syndrome, certain immunodeficiency diseases, repeated respiratory infections, blood transfusion reactions, autoimmune diseases, etc.

3. IgM

IgM is a high-efficiency antibody with strong bactericidal power, especially effective against Gram-negative bacteria such as Escherichia coli. 

Reference value: 0.4~3.5 g/L for adults.

It is the first antibody synthesized and secreted in the process of ontogeny. IgM can be produced in the late stage of fetal development. The content of IgM is minimal in newborns, and it gradually rises at birth, reaching adult levels at 1/2 to 1 years old.

An increase of this antibody in the cord blood indicates that the fetus has an intrauterine infection (such as rubella virus, cytomegalovirus, etc.). The natural blood group antibody is IgM, and the hemolytic reaction caused by blood transfusion of incompatible blood group is also caused by this antibody. When the body is infected by a pathogen, IgM is the earliest antibody produced in the humoral immune response. The clinical detection of this antibody can specifically diagnose and treat the disease early.   

Clinical significance: The increase is seen in macroglobulinemia, autoimmune diseases (systemic lupus erythematosus, rheumatoid arthritis, Sjogren’s syndrome), viral infection, chronic lymphocytic leukemia and malignant lymphoma. Decrease is seen in multiple myeloma, burns, malnutrition and immunocompromised diseases.

4. IgE

IgE is also called reactin. When the body encounters allergens, IgE can cause cells to release a variety of active substances, causing allergic reactions. 

Reference value: 0.13~0.93 g/L for adults.

The normal content is very stable. It is the immunoglobulin with the least content in normal human serum, and has a strong affinity with mast cells, alkaloid granulocytes and other cells, which causes type I hypersensitivity. 

Increased IgE is seen in bronchial asthma, urticaria, eczema and other allergic diseases and parasitic diseases (roundworms, hookworms) and so on. IgE reduction is seen in primary agammaglobulinemia.  

5. IgD

It may have the function of regulating immunity. 

Reference value: 0.6~2.0 g/L for adults.

It is an antibody that can be produced at any time of individual development, but its content in the body is very low, easily hydrolyzed by proteases, and has a short half-life (only 3 days). Its main physiological functions are not yet fully understood.

Clinical significance: Increased IgD can be seen in multiple myeloma, chronic osteomyelitis, epidemic hemorrhagic fever, cirrhosis, certain connective tissue diseases, allergic diseases, Hashimoto's thyroiditis and viral infectious diseases. Decrease can be seen in primary agammaglobulinemia, silicosis, etc.

Conclusion

Measuring the content of human serum immunoglobulin is an important method to understand the immune function of the body and has certain value in the diagnosis of autoimmune diseases, especially for the diagnosis of plasma cell malignant transformation and humoral immune deficiency.

In addition, it has certain value for observing the curative effect of disease. However, serum immunoglobulins have a large range of variation with marginal specificity. Therefore, the diagnosis and analysis of its significance must be closely integrated with clinical diseases.

Want to learn more about antigens and antibodies? Read about monoclonal and polyclonal antibodies.

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What is an immuno-histochemistry test?

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immunohistochemistry

What is immunohistochemistry?

1. Definition

Immunohistochemistry (ihc), also known as immunocytochemistry, refers to a new technology that the qualitative, localized, and quantitative determination of the corresponding antigens is performed through antigen-antibody reaction and histochemical color reaction in tissue cells’ situ by specific antibodies labeled with a chromogenic reagent.

It cleverly combines the specificity of the immune response and the visibility of histochemistry. With the help of the imaging and magnification of microscopes (including fluorescence microscopes and electron microscopes), it can detect various antigenic substances (such as protein, polypeptide, enzymes, hormones, pathogens and receptors, etc.). Immunohistochemistry technology has developed rapidly in recent years. In the 1950s, it was limited to immunofluorescence technology. And since then a highly sensitive and more practical immunoenzyme technology was gradually developed.

2. Rationale

The binding between antibody and antigen has a high degree of specificity, and immunohistochemistry harnesses this principle. Firstly, a certain chemical substance in the tissue or cell is extracted and used as an antigen or hapten. After immunizing the animal, a specific antibody is obtained, and then the antibody is used to detect the same antigen substance in the tissue or cell. Because the complex of antigen and antibody is colorless, it is necessary to show the binding site of antigen and antibody by means of histochemistry to achieve qualitative, localized or quantitative research on unknown antigens in tissues or cells.

3. Characteristics

A. Strong specificity

The basic principle of immunology determines that the binding between antigen and antibody is highly specific. Therefore, immunohistochemistry is theoretically a specific display of antigens in tissue cells. For example, keratin shows epithelial components, and LCA shows lymphocytes. ingredient. Only when there are cross-antigens in the tissue cells, cross-reactions will occur.

B. High sensitivity

In the initial stage of the application of immunohistochemistry, due to technical limitations, only the direct method, indirect method and other less sensitive technologies were available. At that time, the antibody could only be diluted for several times or dozens of times; now the advent of ABC method or SP allows antibodies to be diluted thousands, tens of thousands, or even hundreds of millions of times, and the antibody can still bind to antigens in tissue cells. This highly sensitive antibody-antigen reaction makes immunohistochemistry methods more and more convenient for routine pathological diagnosis.

C. Accurate positioning, combination of form and function

This technology can accurately locate antigens in tissues and cells through antigen-antibody reaction and color reaction, so that different antigens can be positioned and observed in the same tissue or cell at the same time. So the combination of morphology and function can be studied, which is very meaningful to carry out in-depth research in the field of pathology.

4. Classification

5. Function

A. specimen

The experiments mainly use tissue specimens and cell specimens. The former includes paraffin embedding sections (pathological sections and tissue chips) and frozen sections, and the latter includes tissue prints, cell slides and cell smears.

Among them, paraffin section is the most commonly used and most basic method to make tissue specimens. It is well-preserved for tissue morphology and can be used for serial sectioning, which is conducive to various staining control observations; it can also be archived for a long time for retrospective research; It will have a certain impact on antigen exposure, but antigen retrieval can be performed, which is the preferred method of tissue specimen preparation in immunohistochemistry.

B. antibody

The commonly used antibodies in immunohistochemical experiments are monoclonal antibody and polyclonal antibody. Monoclonal antibodies are antibodies secreted by a B lymphocyte clone and are prepared by immunizing animals with cell fusion hybridoma technology. Polyclonal antibody is immune serum obtained from animal blood after the purified antigen is directly immunized. It is a mixture of antibodies produced by multiple B lymphocyte clones.

C. Common dyeing methods

According to the different markers, it is divided into immunofluorescence method, immunoenzyme labeling method, and affinity histochemistry method. The latter is a detection method based on a substance with a high affinity for a certain tissue component. This method is more sensitive and facilitates the localization of trace antigens (antibodies) at the cellular or subcellular level. Among them, the biotin-avidin staining method is the most commonly used.

What is immunohistochemistry used for?

Immunohistochemical staining has a very broad role in biomedical research and involves many research fields. However, immunohistochemistry technology also has its limitations. For example, the test substance in the tissue cells must be antigenic, and a certain concentration is required. The detected immunoreactive protein cannot be determined to be newly synthesized by the cell or transported through cells.

Therefore, these characteristics should be fully considered in experimental design. If the experiment needs to prove what kind of cell the known protein is synthesized by, molecular in situ hybridization technology is preferred. In order to guide beginners to use immunohistochemistry technology reasonably and skillfully in experimental design, the basic principles of its application are briefly described as follows:

  1. Determine the cell type and morphology. Some proteins in tissue cells have tissue specificity, such as glial fibrillary acidic protein (GFAP) only exists in astrocytes. Neurofilament (Neurofilament, NF) exists only in nerve cells. These tissue-specific proteins are usually referred to as labeled proteins (Proteiniliaker). The cell type can be determined by the specific antibody of the labeled protein.

    Some cells (such as Langerhans cells and melanocytes in the epidermis) are not easy to identify under a light microscope. By performing immunohistochemical staining on specific proteins in the cytoplasm, the outline of such cells can be clearly displayed. This effect is particularly necessary in neuroscience research and tumor clinicopathology.
  2. Identify the source of cell products. View certain cell products as antigens, prepare corresponding antibodies, and perform immunohistochemical staining on tissue cells to determine the source of cell products. For example, most of the hormones produced by endocrine cells can be identified by immunohistochemical staining techniques. Based on this, the secretory function of cells and the classification of endocrine tumors can be studied, and tumors that secrete ectopic hormones can be detected to understand the degree of cell differentiation.
  3. Determine the degree of cell differentiation. Different cells of the same type express different marker proteins, and the differentiation degree of the cells can be determined according to the identification of these different proteins. For example, the hallmark protein of neuroepithelial cells is nestin, which expresses vimentin when it differentiates into radial glial cells. In the neurogenesis phase, it expresses Ⅲβwhen it differentiates into neuroblasts neural tubulin (TUJl) and neurofilament (NF) when neuroblasts differentiate into mature neurons.
  4. Track the nerve fiber bundle and its projection area. The immunohistochemical method is often combined with the axoplasmic transport tracing method to study the connections between neurons. The axoplasmic transport tracing method uses certain substances that can be taken up by nerve endings. Use histochemical method to show the outline of neurons. Commonly used tracers include horseradish peroxidase and fluorescent gold.

    E.g. The aim is to observe the projection of nerve fibers from a nucleus in the peripheral nervous system or central nervous system. Firstly, the tracer is injected into the nerve fiber end of the animal to allow the animal to survive for a period of time. The material is taken from the expected nerve fiber projection site, and the tracer is located by the histochemical method, and then the immunohistochemical method is implemented to determine its nature.
  5. Application in clinical pathology. Such as identifying the nature of the lesion, discovering small lesions, exploring the origin or differentiated phenotype of the tumor, determining the tumor stage, guiding treatment and prognosis, assisting in the diagnosis and classification of diseases, and searching for the cause of infection, etc.

Immunohistochemitry Protocol

1. Immunofluorescence method

It is the earliest established immunohistochemistry technique. It uses the principle of antigen-antibody specific binding. First, the known antibody is labeled with fluorescein, which is used as a probe to check the corresponding antigen in the cell or tissue. If you observe it under a fluorescence microscope, it will emit fluorescence of a certain wavelength when the fluorescein in the antigen-antibody complex is irradiated by the excitation light, it. Then the localization of a certain antigen in the tissue can be determined, and quantitative analysis can be performed. Because of its strong specificity, high sensitivity, quickness and simplicity, immunofluorescence technology is widely used in clinical pathological diagnosis and testing.

Application

2. Immunoenzyme labeling method

The immunoenzyme labeling method is a technique developed in the 1960s followed by immunofluorescence. The basic principle is to first use enzyme-labeled antibodies to interact with tissues or cells, and then add enzyme substrates to generate colored insoluble products or particles with a certain electron density.

Through light or electron microscopy, various types of cell surfaces and antigen component in cells is subject to localization research. Immunoenzyme labeling technology is the most commonly used technology. The main advantages of this method compared with immunofluorescence technology are: accurate positioning, good contrast, long-term preservation of stained specimens, and suitable for optical and electron microscopy studies.

The immunoenzyme labeling method has developed very rapidly, and a variety of labeling methods have been derived. With the continuous improvement and innovation of the method, its specificity and sensitivity have been greatly improved, more convenient to use. ABC's method, SP three-step method, ready-to-use two-step method detection systems are widely used in pathological diagnosis.

Application

3. Immune colloidal gold technology

The immune colloidal gold technology uses a special metal particle such as colloidal gold as a marker. Colloidal gold refers to the hydrosol of gold, which can adsorb proteins quickly and stably with no obvious effect on the biological activity of the protein. Therefore, using colloidal gold-labeled primary antibody, secondary antibody, or other molecules that specifically bind to immunoglobulins (such as staphylococcal protein A) as probes, can qualitatively locate, or even quantify antigens in tissues or cells.

Since colloidal gold has particles of different sizes and the electron density of colloidal gold is high, the immuno-colloidal gold technique is particularly suitable for single-label or multi-label localization studies of immunoelectron microscopy. And because of the color of colloidal gold from light red to deep red, it is also suitable for light microscope observation. Such as the application of silver-enhanced immunogold and silver law is more convenient for light microscope observation.

Conclusion

Because of its own unique characteristics, immunohistochemistry technology has become a technique often selected by the majority of scientific researchers in tissue cell positioning, qualitative and quantitative research. Therefore, with the update of scientific research tools, scientists need to have a more extensive and in-depth understanding of immunohistochemistry, optimize the design of technical routes, and promote the further development of immunohistochemistry technology.

Want to learn more about antigens and antibodies? Read about FC stand information.

References

What is the function of immunoglobulin?

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immonoglobuline a
immonoglobuline a

What is immunoglobulin?  

1. Definition

Globulin is a serum protein that exists in the human body and has an immune effect. It is also called immunoglobulin. When the human immune system encounters foreign invaders, it will produce different amounts of globulin according to the characteristics of the invader. If the invader is difficult to eliminate, it will stimulate the lymphatic system to produce more antibody until the invader is destroyed. You can see the immunoglobulin structure thereinafter.

2. Immunoglobulin Structure

Through X-ray crystal diffraction structure analysis, it is found that the basic structure of immunoglobulin is a monomer composed of 4 symmetrical polypeptide chains connected by disulfide bonds. The two chains with larger molecular weight are called heavy chains. The two smaller molecular weight chains are called light chains.

The sequence of about 110 amino acids near the amino terminus (N-terminus) of the globulin heavy chain and light chain varies greatly, called the variable region (V region), which accounts for 4 (or 1/5) and 1/2 of the heavy chain and light chain respectively. The H chain and L chain of this region each has 3 amino acid composition and arrangement sequence.

The hinge area is located between CH1~CH2, which is sensitive to protease and is easily hydrolyzed. It is rich in proline, so it is easy to stretch and bend, which is beneficial for the two arms to bind two epitopes at different distances at the same time.

3. Five types of immunoglobulin

  1. According to the target, it can be divided into anti-toxin, antibacterial antibody, anti-viral antibody and cytophilic antibody (immunoglobulin that can bind to cells, such as lgE reagin antibody in type 1 allergy, which can be attached on target cell membrane).
  2. According to physical and chemical properties and biological functions, immunoglobulins are divided into five categories, namely immunoglobuling g (IgG), immunoglobuling a (IgA), immunoglobuline m (IgM), immunoglobulin D (IgD) and Immunoglobuline E (IgE).
    1. IgM antibodies are the first antibodies secreted in an immune response. They initiate a cascade of complement reactions after binding to the antigen. They also connect the invaders to each other and gather them into a pile for the phagocytosis of macrophages;
    2. Igg antibodies activate complement and neutralize a variety of toxins. IgG lasts for the longest time and is the only antibody that can pass through the placenta to protect the fetus during pregnancy. They also secrete into colostrum from the mammary glands to protect the newborn;
    3. IgA antibody enters the mucosal surface of the body, including the mucous membranes of respiratory, digestive, and reproductive channels, and neutralizes infectious agents. This antibody can also be transported to the mucosa of the digestive tract of newborns through colostrum of breast milk. It is the most important type of antibody in breast milk;
    4. The tail of the Ige antibody binds to the cell membrane of basophils and mast cells. When the antibody binds to the antigen, basophils and mast cells release substances such as histamine to promote the development of inflammation. This is also the antibody that triggers immediate allergic reactions;
    5. IgD antibodies mainly appear on the surface of mature B lymphocytes, which may be related to the differentiation of B cells. IgD was discovered from human myeloma protein in 1995. It has a molecular weight of 175kD and is mainly produced by plasma cells in tonsils and spleen. The concentration of IgD in human serum is 3-40μg/ml, which is less than 1% of total serum Ig. It is synthesized late in individual development. IgD has a long hinge region and is sensitive to protease hydrolysis, so IgD has a short half-life of only 2.8 days. The exact immune function of IgD in serum is still unclear. During the stage of B cell differentiation to mature B cell, in addition to expressing SmIgD, immune tolerance appears after antigen stimulation. SmIgD gradually disappears after mature B activation or its becoming memory B cells.
  3. According to whether there is a visible reaction after binding to the antigen, it can be divided into: a complete antibody with a visible binding reaction under the participation of the medium, commonly referred to as an antibody. And an incomplete antibody without visible reaction that succeeds in inhibiting the combination of antigen and its corresponding complete antibody.
  4. According to sources, antibodies can be divided into natural antibodies and immune antibodies.

Immunoglobulin vs Antibody

1. What is antibodies? 

Antibody refers to the immunoglobulin that is produced by the plasma cells differentiated from B lymphocytes under the stimulation of antigen by the body's immune system and can specifically bind to the corresponding antigen.

2. Antibody Structure

Antibodies have a symmetrical structure with 4 polypeptide chains, of which 2 are the same heavy chain (H chain) with longer and larger relative molecular weight; and 2 are the same light chain (L chain) with shorter and smaller relative molecular weight. The chains are connected by disulfide bonds and non-covalent bonds to form a monomer molecule composed of 4 polypeptide chains. There are two types of light chains: κ and λ, and five types of heavy chains: μ, δ, γ, ε, and α. The entire antibody molecule can be divided into two parts, the constant region and the variable region.

In a given species, the constant regions of different antibody molecules all have the same or almost the same amino acid sequence. The variable region is located at the end of the two arms of "Y". In the variable region, there is a small part of amino acid residues that change particularly strongly, and the composition and sequence of these amino acid residues are more prone to variation. The region is called hypervariable region.

The hypervariable region is located on the surface of the molecule and consists of at most 17 amino acid residues, and 2-3 at least. The amino acid sequence of the hypervariable region determines the specificity of the antibody binding to the antigen. The two antigen binding sites on an antibody molecule are the same, located at the ends of the two arms, called antigen-binding fragments (Fab). The handle of "Y" is called crystalline fragment (FC), and the sugar is bound to FC.

3. The difference between antibodies and immunoglobulins   

In 1964, the World Health Organization held a special meeting, referring to the globulins with antibody activity and antibody-related as immunoglobulins (Ig), such as myeloma protein, macroglobulinemia, cryoglobulinemia and other patients’ serum abnormal immunoglobulins and subunits of immunoglobulins naturally occurring in normal people. Therefore, immunoglobulin is a concept of structural chemistry, and antibody is a concept of biological function. It can be said that all antibodies are immunoglobulins, but not all immunoglobulins are antibodies.

The function of immunoglobulin 

immunoglobulin structure
immunoglobulin structure

1. IgM

IgM is the first type of Ig synthesized by the fetus, accounting for 5%-10% of the total serum immunoglobulin. The serum concentration is about 1mg/ml.

Monomer IgM is expressed on the cell surface as a membrane-bound type (mIgM), which constitutes the B cell antigen receptor (BCR).

Secreted IgM is a pentamer, the Ig with the largest molecular weight with 19S of the sedimentation coefficient. It is called macroglobulin, which generally cannot pass through the blood vessel wall and mainly exists in the blood.

Pentameric IgM contains 10 Fab segments with strong antigen binding capacity. It contains 5 Fc antibody segments, which activate complement more easily than igg antibodies. The natural blood group antibody is IgM, and blood transfusions with incompatible blood types can cause severe hemolytic reactions. IgM is the first antibody synthesized and secreted in the process of ontogeny. The fetus can produce IgM in the late embryonic development period.

Therefore, the rise of IgM in the cord blood indicates that the fetus has an intrauterine infection (such as rubella virus or cytomegalovirus infection). IgM is also the earliest antibody that appears in the initial humoral immune response, and is the body's "vanguard" against infection. The detection of IgM in the serum indicates the recent occurrence of infection and can be used for early diagnosis of infection. IgM on the membrane surface is the main component of B cell antigen receptors.

IgM appears first during the infection process, but it does not last long as a sign of recent infection.

2. IgG

IgG is the abbreviation of immunoglobulin G (IgG), is the main antibody component of serum, accounting for about 75% of serum Ig. Among them, 40-50% are distributed in serum, and the rest are distributed in tissues. IgG is the only immunoglobulin that can pass through the placenta. The functional role of IgG mainly plays a protective role in the body's immunity, most of which are antibacterial and antiviral. It can effectively prevent corresponding infectious diseases in response to measles and hepatitis A. Its indicators are of significance for the diagnosis of certain diseases.

3. IgA

The content of immunoglobuline A (IgA) in normal human serum is second only to IgG, accounting for 10-20% of serum immunoglobulin content. From the structure point of view, IgA has monomers, dimers, trimers and multimers. According to its immune function, it is divided into serotype and secretory type. Serotype IgA exists in serum, and its content accounts for about 85% of total IgA. Although serotype IgA has certain functions of IgG and IgM, it does not show important immune functions in the serum.

Secreted IgA exists in secretions, such as saliva, tears, colostrum, nasal and bronchial secretions, gastrointestinal fluids, urine, sweat and so on. Secreted IgA is the main antibody of the body's mucosal local anti-infection immunity. Therefore, it is also called local mucosal antibody. IgA cannot pass through the placenta. There is no IgA antibody in the neonatal serum, but secreted IgA can be obtained from breast milk. In 4 to 6 months after the birth of a newborn, IgA may appear in the blood, and it will gradually increase in the future, reaching a peak in adolescence.

4. IgE

IgE is a secreted immunoglobulin with a molecular weight of 196,000 and consists of two light chains and two heavy chains. It is produced by plasma cells in the lamina propria of the nasopharynx, tonsils, bronchi, gastrointestinal mucosa, etc. It is the main antibody that causes type I allergic reactions. The most obvious basic biological characteristic is that it is homologous. Human IgE only can sensitize human and monkey cells, and no other animals. IgE is the most sensitive to heat among the immunoglobulins.

Among the five immunoglobulins, IgE has the shortest half-life, the highest decomposition rate and the lowest synthesis rate, so it accounts for the lowest percent in the serum. The IgE value in normal human serum is about 0.1-0.9 mg/L, and it is usually slightly higher in men than in women. IgE in serum is significantly higher in patients with allergies or hypersensitivity than that in normal people, and patients with exogenous asthma are several times higher than normal people. Therefore, high levels of IgE in the serum often indicate the presence of genetic allergies or type I allergies.

5. IgD

Serum immunoglobuline D (IgD) content is very low, it can exist as a membrane receptor on the surface of B cells, and its role may be involved in initiating the production of antibodies by B cells. Its function is also related to certain autoantibodies and anti-toxin antibodies, such as anti-nuclear Antibodies, anti-basement membrane antibodies, anti-thyroid antibodies, anti-diphtheria toxoid antibodies, and tetanus toxoid antibodies are related.

Conclusion

From this passage, we can know the immunoglobulin structure and its function. Antibodies can combine with antigens (both foreign and self) to effectively remove foreign invaders such as microorganisms and parasites, neutralize the toxins they release or remove certain self-antigens, so that the body maintains a normal balance.

But sometimes it also causes pathological damage to the body, such as the production of some autoantibodies such as anti-nuclear antibodies, anti-double-stranded DNA antibodies, and anti-thyroglobulin antibodies, which would be deleterious to the human body.

References

What is the difference between monoclonal and polyclonal antibodies?

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What are monoclonal antibodies?

1. Definition

There is a big difference between monoclonal and polyclonal antibodies. Monoclonal antibodies are highly uniform antibodies that are produced by a single B cell clone and target only a specific epitope. Hybridoma antibody technology is based on cell fusion technology, which combines sensitized B cells and myeloma cells with immortal reproduction capacity into B cell hybrids tumor.

A single hybridoma cell with this characteristic is used to cultivate a cell population to prepare a specific antibody against an epitope, that is, a monoclonal antibody.

2. History

The development of monoclonal antibodies has gone through four stages, namely:
Murine monoclonal antibodies, chimeric antibody, humanized monoclonal antibody and fully human monoclonal antibodies.

Fully human monoclonal antibodies: The variable region and constant region of the antibody are of human origin, eliminating immunogenicity and toxic side effects.

The related technologies for the preparation of fully human antibodies mainly include:
Human hybridoma technology, EBV transformation B lymphocyte technology, phage display technology, transgenic mouse antibody preparation technology and single B cell antibody preparation technology.

Humanized and fully humanized antibodies drugs prepared from humanized and fully humanized antibodies overcome various shortcomings of animal-derived antibodies and chimeric antibodies because of their high affinity, high specificity, and low toxic and side effects. It has become an inevitable trend in the development of therapeutic antibody drugs.

3. Monoclonal Antibody Production

  1. Immunize animals
    Immunization of animals is the process of immunizing mice with the target antigen to make the mice produce sensitized B lymphocytes. Generally, female BALB/c mice aged 6-8 weeks are selected and injected according to the pre-established immunization protocol. The antigen enters the peripheral immune organs through the blood circulation or lymphatic circulation, stimulates the corresponding B lymphocyte clones, activates, proliferates, and differentiates into sensitized B lymphocytes.
  2. Cell Fusion
    The mice are killed with carbon dioxide, and the spleen is taken out aseptically. Then squeeze and ground it in a petri dish to make a spleen cell suspension. The prepared syngeneic myeloma cells and mouse spleen cells are mixed in a certain proportion, and add the fusion promoter polyethylene glycol. Under the role of polyethylene glycol, various lymphocytes can fuse with myeloma cells to form hybridoma cells.
  3. Selective cultivation
    The purpose of selective culture is to screen fused hybridoma cells, and HAT selective medium is generally used. In the HAT medium, the unfused myeloma cells die due to lack of hypoxanthine-guanine-phosphoribosyltransferase and unavailable salvage pathway to synthesize DNA.

    Although unfused lymphocytes have hypoxanthine-guanine-phosphoribosyltransferase, they cannot survive for long time in vitro.

    Only the fused hybridoma cells can survive and proliferate in HAT medium because they have obtained hypoxanthine-guanine-phosphoribosyltransferase from spleen cells and the ability of unceasing proliferation from myeloma cells.
  4. Screening and cloning of hybridoma positive clones
    Only a few of the hybridoma cells grown in HAT medium are cells that secrete predetermined specific monoclonal antibodies. Therefore, screening and cloning are necessary. The limiting dilution method is usually used for clonal culture of hybridoma cells. Using sensitive, rapid, and specific immunological methods, the positive hybridoma cells that can produce the required monoclonal antibodies are screened out and cloned and expanded. After a comprehensive identification of the immunoglobulin type, subclass, specificity, affinity, epitope of the recognized antigen and its molecular weight of the monoclonal antibody secreted by it, it should be frozen in time.
  5. Mass production of monoclonal antibodies
    The large-scale preparation of monoclonal antibodies mainly adopts animal in vivo induction and in vitro culture methods.

4. Cloning Method

The positive wells that have been tested for antibodies can be cultured and cloned to obtain monoclonal antibodies secreted by the offspring of a single cell. Generally speaking, the earlier the cloning time, the better. Because during this period, various hybridoma cells grow vigorously at the same time, competing for nutrition and space, and the cells producing the specified antibodies may be submerged and eliminated.

However, the cloning time should not be too early, otherwise the cell traits are unstable, and the number of cells is small and easy to lose. The cloned positive hybridoma cells, after a period of culture, will also lose the ability to produce antibodies due to cell mutations or loss of specific chromosomes, so they need to be cloned again and again. The number of cloning is determined by the secretion ability and the immunity of the antigens. Generally speaking, the number of clones of a strong immune antigen can be less, but at least 3 to 5 clones can make it stable. There are many methods of cloning, including limiting dilution method, micromanipulation method, soft agar plate method and fluorescence activation separation method.

monoclonal-and-polyclonal-antibodies
monoclonal-and-polyclonal-antibodies

5. Application

Since the advent of monoclonal antibodies, they have been applied in many fields of medicine due to their unique characteristics.

  1. Laboratory medicine diagnostic reagents
    As a diagnostic reagent in laboratory medicine laboratories, monoclonal antibodies are widely used in technologies such as enzyme-linked immunosorbent assay, radioimmunoassay, immunohistochemistry and flow cytometry due to their strong specificity, high purity, and good uniformity. And the application of monoclonal antibodies has greatly promoted the development of commercial kits.

    Commercial kits made of monoclonal antibodies are widely used in:
    1. Detection of pathogenic microorganism antigens and antibodies;
    2. Detection of tumor antigens;
    3. Detection of immune cells and their subgroups;
    4. Hormone determination;
    5. Determination of cytokines.

      The recognition of antigens by monoclonal antibodies is very different from that of polyclonal antibodies. Different kits use different monoclonal antibodies and have different antigen recognition sites, leading to certain differences in test results. Therefore, the standardization issue needs further study.
  2. Purification of protein
    Monoclonal antibodies are important ligands in affinity chromatography. The monoclonal antibody is adsorbed on an inert solid phase matrix (such as Spehrose 2B, 4B, 6B, etc.) and prepared into a chromatography column. When the sample flows through the chromatographic column, the antigen to be separated can specifically bind to the solid phase monoclonal antibody, and the remaining components cannot bind to it. After the chromatographic column is fully eluted, the ionic strength or pH of the eluate is changed, the antigen to be separated is dissociated from the antibody, and the antigen to be purified can be obtained by collecting the eluate.
  3. Tumor-oriented therapy and radioimmunoimaging technology
    The monoclonal antibody directed against a certain tumor antigen is connected with a chemotherapy drug or radiotherapy substance, and the targeting effect of the monoclonal antibody is used to carry the drug or radiotherapy substance to the target organ and directly kill the target cell, which is called tumor-directed therapy.

    In addition, radioimmunoimaging can be performed by connecting radioactive markers with monoclonal antibodies and injecting them into patients to assist in tumor diagnosis. Monoclonal antibodies are mainly murine antibodies, and the serum of heterogeneous animals can cause allergic reactions in humans. Therefore, the preparation of human-human monoclonal antibodies or humanized antibodies is more important, but no significant progress has been made in this regard.

What is polyclonal antibody? 

1. What does polyclonal antibody mean?

Antigens are usually composed of multiple antigenic determinants. One type of antigenic determinant stimulates the body, and the antibody produced by a B lymphocyte receiving the antigen stimulation is called Monoclonal Antibody. The body is stimulated by multiple antigenic determinants, and various monoclonal antibodies are produced accordingly. These monoclonal antibodies are mixed together to form polyclonal antibody.

2. Structure

The molecular structure on the antigen that can cause the body to produce antibodies is called epitope. There can be several different antigenic determinants on an antigen, so that the body produces several different antibodies, and the final antibodies are plasma cells. A plasma cell population that only acts on one antigenic determinant is a clone. The specific antibody produced by a clone is called a monoclonal antibody. Monoclonal antibodies can specifically bind to a single specific antigenic determinant, just as a missile accurately hits the target. On the other hand, even if it is the same antigenic determinant, several clones can produce antibodies in the body, forming a mixture of several monoclonal antibodies, called polyclonal antibodies.

3. Classification

Antigens are usually composed of multiple epitopes. One type of epitope stimulates the body. The antibody produced by a B lymphocyte receiving the antigen is called a monoclonal antibody. The body is stimulated by a variety of antigenic determinants, and a variety of monoclonal antibodies are produced accordingly. These monoclonal antibodies are mixed together to form polyclonal antibodies. Except for diverse antigenic determinants, the same type of epitope can also stimulate the body to produce five types of antibodies: IgG, IgM, IgA, IgE and IgD.

Polyclonal antibodies are a group of immunoglobulins secreted by the body's plasma cells that stimulated by heterologous antigens (macromolecular antigens, hapten conjugates). Polyclonal antibodies are widely used in research and diagnosis due to their ability to recognize multiple epitopes and cause precipitation reactions with short preparation time and low cost.

4. Application

A good polyclonal antiserum contains multiple antibodies against different epitopes of a certain antigen. Since polyclonal antiserum usually contains antibodies against different epitopes of a certain antigen, including denatured-resistant epitopes, it will also have an effect in deep-fixed samples. In the staining of paraffin-embedded tissue sections, Polyclonal antibodies are often used. According to the different needs of the experiment, polyclonal antibodies are used to label the corresponding antigen.

In addition, in agricultural production, polyclonal antibody is used for on-site monitoring of pesticide residues; in clinical applications, polyclonal antibodies are mainly used for pathogen detection, disease diagnosis and treatment, such as protein immunosuppressants for transplantation response and treatment of autoimmune diseases.

Monoclonal vs Polyclonal antibodies

1. Concept

Cloning: refers to asexually reproduced cell line, which is a cluster of cell lines formed by the division and reproduction of a single progenitor cell. In all members of this family, if no mutation occurs, the genes are exactly the same.

Polyclonal antibody (pAb): Immunize animals with an antigen containing multiple epitopes, which can stimulate multiple B cell clones to produce different antibodies against multiple epitopes. The obtained immune serum is actually a mixture of multiple antibodies.

Monoclonal antibodies (mAb): Homologous antibodies produced by a clone of B cells that recognize an epitope. Highly uniform, strong specificity, high titer, little or no cross-reactivity.

2. Production

Differences from monoclonal antibody preparation:
B lymphocytes treated with specific antigens and myeloma cells are fused to obtain hybridoma cells. After screening by HAT medium and detecting the titer by ELISA, a positive clone is obtained, and then do a cell culture or inject the cells into the abdominal cavity of animals (usually balb/c mice) and culture them with ascites, collect the supernatant/ascites and purify them to obtain monoclonal antibodies.

The preparation of polyclonal antibody is not as cumbersome as monoclonal antibodies. You only need to inject the antigen (the higher the purity, the better) directly into the animal body for immunization. After 3 to 4 immunizations, the titer is qualified by ELISA, and the blood is centrifuged. The supernatant can be purified to obtain polyclonal antibodies. Therefore, the preparation cycle of polyclonal antibodies is shorter than that of monoclonal antibodies, and the initial preparation price is lower than that of monoclonal antibodies.

3. Cons and Pros

A. Monoclonal antibody

Advantages:

Excellent affinity and purification:

B. Polyclonal antibody

Advantages:

Disadvantages:

4. Other differences

CharacteristicsMonoclonal AntibodyPolyclonal Antibody
1SpecificityStrongWeak
2StabilityRelatively poor, sensitive to physical and chemical conditionsGood
3Requirements for immunogensImpure immunogens can also produce highly purified antibodiesHigh immunogen purity is required
4StandardizationEasy to standardize,
little difference between batches
Difficult,
big differencebetween batches
5RecognitionOnly one epitope on the antigen is detectedCan recognize multiple epitopes
6Cross Reactionnot easy to cross react with other proteinscommon and difficult to avoid nonspecific reactions
7Precipitation and agglutinationMost don'tCommon
8Production CostHighLow
9Preparation PeriodLongShort
10PriceHighLow

Conclusion

The gap between monoclonal and polyclonal antibodies is enormous, and these differences make them useful in different fields. Monoclonal antibodies occupy a vital place in medicine, while polyclonal antibodies shine in the fields of agricultural production and disease detection and treatment.

References

What does FC stand for in antibody?

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What is antibodies?
What is FC antibody?
1. Definition
2. Fc Domain
3. Brief Introduction
What does Fc receptor stand for?
What does FC stand for in antibody?

Conclusion

The crystallizable fragment (Fc antibody) is the tail of the antibody, which interacts with cell surface receptors called Fc receptors and some proteins of the complement system. This feature allows antibodies to activate the immune system.

In IgG, IgA and IgD antibody isotypes, the Fc antibody is composed of two identical protein fragments derived from the second and third constant domains of the two heavy chains of the antibody; IgM and IgEFc regions contain three heavy chain constant domains (CH domains 2-4) in each polypeptide chain. The Fc region of IgG has a highly conserved N-glycosylation site. Glycosylation of Fc fragments is essential for Fc receptor-mediated activity.

What is antibodies?

Antigen vs Antibody
Antigen vs Antibody

Antibodies are immunoglobulins, which are globulins that have antibody (Ab) activity or chemical structure and are similar to antibody molecules. Generally, it is a peptide chain structure composed of two identical light chains and two identical heavy chains connected by interchain disulfide bonds.

Antibodies can be divided into five categories, namely immunoglobulin G (IgG) and immunoglobulin A (IgA), immunoglobulin M (IgM), immunoglobulin D (IgD) and immunoglobulin E (IgE). And antibody is composed of variable region Fab and constant domain Fc. Fab can bind antigen, and Fc can bind to Fc receptors. Take IgG as an example. IgG usually wanders in the blood and binds to the Fc receptors on the surface of immune cells. It will function to stimulate immune cells and resist invading pathogens.

What is FC antibody?

1. Definition

Fc receptors can bind to IgFc fragments on the cell membrane surface. The receptors that bind to different immunoglobulins (IgA, IgE, IgM, and IgG) are collectively called FcRs, which are involved in the regulation and execution of antibody-mediated immune responses.

Generally speaking, FcRs connect the effector regions triggered by specific adaptive immune system and innate immune cells (mast cells, neutrophils, monocytes and macrophages). More importantly, these pro-inflammatory responses are closely related to regulating the body from tissue damage. After binding to the Fc region of antibody to activate the signaling pathway, immune cells will start a series of immune responses, such as: antibody-producing cell restriction factors, inflammatory factors, or antibody-dependent cell-mediated cytotoxicity (ADCC) and other killing targets cell.

Fc receptor is the receptor for the c-terminus of the Fc part of immunoglobulin. After the immunoglobulin (Ig) binds to the antigen, the Fc region of antibody is allosteric and binds to the Fc receptor on the cell membrane to produce various biological effects. The effect of the antigen-antibody complex on the cell is all mediated by the Fc receptor. Therefore, fc antibody receptors play a very important role in immune function and its regulation. Each type of Ig has its corresponding Fc receptor.

2. Fc Domain

The positions of the two antigen-binding parts on an antibody molecule are the same, and they are located at the ends of the two arms called antigen-binding fragments (Fab antibody). The handle of "Y" is called crystalline fragment (FC), and the sugar is bound to FC. Fc (crystallizable fragment) consists of: 2 CH2, 2 CH3 (IgA, IgD, IgG), a total of 4 domains, or 2 CH2, 2 CH3, 2 CH4 (IgM, IgE), a total of 6 Structure domains.

3. Brief Introduction

Through the use of Fab'2 antibody fragments and P, c receptor-deficient mice to further understand the role of fc antibody in the infiltration of macrophages. Studies using Fab'2 anti-GBM antibody fragments indicate that Fc region must be used in autoantibody-dependent and complement-independent macrophage infiltration.

The use of IgG and Fc fragment to treat mouse immune complex-mediated proliferative glomerulonephritis can reduce the progression of the disease and reduce the infiltration of macrophages and T cells. Fcγ receptor (Fc'/R)-deficient mice have been used to study the effect of binding of antibody Fc/FcγR to the receptor on the infiltration of inflammatory cells in glomerulonephritis. Compared with intact NZB/NZW mice, FcγR-deficient lupus-prone mice have reduced crescent formation and improved survival, but the degree of immune complex and complement deposition is similar. This is consistent with the results of previous studies that complement is not necessary in immune complex glomerulonephritis, indicating that Fc/FcγR mediates macrophage infiltration in immune complex nephritis.

Non-crescent nephritis with defects in anti-GBM and FcRγ chains is characterized by increased survival rate and reduced nephritis. Other studies have shown that FcRγ chain-deficient mice are protected from early neutrophil-related damage, but later develop into proteinuria with macrophage infiltration, accompanied by crescent formation. The FcγRIIB receptor participates in the "antibody feedback" process, which plays an important role in peripheral tolerance. Rats deficient in this inhibitory receptor can easily progress to pulmonary hemorrhage and crescentic glomerulonephritis after immune response to bovine type IV collagen disease.

Glomerulonephritis occurs in the absence of C3 deposition, and the transfer of spleen cells instead of B cells from FcγRIIB-deficient mice can also cause glomerulonephritis, indicating that sensitizing T cells play a significant role here. Lupus-prone to murine FcγRIIB promoter polymorphism is related to the production of autoantibodies.

What does Fc receptor stand for?

For cells with its receptor, when the antibody binds to the antigen, the cell will exert the following special functions:

  1. Prophage has Fc receptors for IgG, and neutrophils accounting for most of polymorphonuclear leukocytes have Fc receptors for IgG and IgA. Antigens are usually captured and swallowed by antibodies that bind to antigens and sometimes free antibodies (cytophilic antibodies).
  2. The majority of B cells (over 80%) have Fc receptors for IgG. And they do not differentiate into antibody-producing cells, and can be activated by binding to antigen-antibody complexes to release antibody-producing cell restriction factors.
  3. About 10% of T cells have Fc receptors, which mainly act as immune response regulating cells, but the role of Fc receptors in these cells is still unclear. In the human body, cells that have Fc receptors for IgM are helper cells for B cells, and cells that have receptors for IgG function as inhibitory cells.
  4. When IgE that binds to the Fc receptor of mast cells further binds to the antigen, the mast cells can release factors that cause "immediate type" allergies.
  5. Certain non-lymphocytic cells (NK cells) can bind to the FC region of IgG that binds to cancer cells and heterogeneous cells, and hinder these cells. This phenomenon is called antibody-dependent cell-mediated cytotoxicity (Antibody dependent cell-mediated cytotoxicity). In immunology, cells with Fc receptors generally include B cells, killer cells, and macrophages.

What does FC stand for in antibody?

Different Ig subclasses interact with different types of cells through a complex family of Fc receptors on the cell surface. The affinity, cell distribution, structure, and biological effects of these Fc receptors with Ig are also different. Once FcR binds to the IgFc segment, it will transmit special intracellular signals and induce various cellular responses. These responses depend on the FcR type, cell type, cell activation state, costimulatory response, number of receptors involved, receptor cross-linking, and other external factors that affect the Fc fragment of antibodies.

The relative balance of inhibitory receptors (FcγRⅡ) and activated (FcγRI and FcγRⅢ) FcRs expressed by leukocytes and parenchymal cells is the main regulator of inflammatory response caused by antibody deposition and the main determinant of disease susceptibility.

Both mouse and human IgG receptors and FCγRs are members of the Ig superfamily. It is divided into three types, including high-affinity FcγRI (CD64), which can bind to monomeric IgG; low-affinity FcγRⅡ (CD32) and FcγRⅢ (CD16), which only interact with IgG complexes. Variations of multiple genes and alleles and selective splicing of mR-NA have resulted in a variety of different FcγR types, and their transmembrane and cytoplasmic regions are significantly different, leading to functional heterogeneity. This heterogeneity is also reflected in the individual FClrR type and IgG subclass (especially human IgGl and IgG2) binding ability is different. The expression of FcγRs varies with the state of cell activation and is regulated by cytokines.

IgE Fc receptors (FcεR) are divided into two types, including high-affinity FcεRI (a member of the Ig superfamily) and low-affinity FcεRⅡ (CD23, a member of the serum lectin family). The latter is distributed on the surface of a variety of hematopoietic cells, including B cells, which is the corresponding receptor for CD21 (complement receptor 2, CR2, which is involved in regulating the threshold of B cell receptor signaling). Human FcεRⅠReceptors are members of the Ig superfamily which can bind monomeric or multimeric IgAl and IgA2, and are widely distributed in various cells.

Different glycosylation structures lead to different phenotypes. Human mesangial cells express a new bone marrow IgA receptor that is different from CD89. Its binding to IgA triggers the expression of cytokines and chemokines, cell proliferation, and the synthesis of extracellular matrix. Soluble FcRs are derived from the secretion of proteolytic fragments on the cell surface or selective splicing products of mRNA lacking a transmembrane region. They are involved in immune regulation (that is, the inhibitory effect of Ig products in vitro), and can also have a therapeutic effect on hypersensitivity caused by antibody.

Conclusion

FC antibody binds to FC receptors, allowing antibodies to successfully activate the immune system and help us fight off foreign invaders. It can be seen that FC antibody plays an irreplaceable role in human life and health.

Want to learn more about antigens and antibodies? Read Monoclonal-and-polyclonal-antibodies.

References

What is the difference between serum and plasma?

Blood test is a great rapid test for COVID-19 detection. The different specimens will have big different final results while doing covid-19 antibody test. All rapid test will require to detect based on whole blood, plasma or serum. So, what’s the difference between serum and plasma? Serum VS Plasma as below.

What does blood consist of?

Blood consists of plasma and blood cells.

(1) Plasma

Plasma is equivalent to the intercellular substance of connective tissue. Serum is a light yellow translucent liquid. In addition to a large amount of water, plasma contains inorganic salts, fibrinogen, albumin, globulin, enzymes, hormones, and various nutrients, etc. These substances do not have a certain shape, but have important physiological functions.

1L of plasma contains 900~910g water (90%~91%), 65~85g protein (6.5%~8.5%) and 20g low molecular substance (2%). There are many electrolytes and small molecular organic compounds in low molecular substances, such as metabolites and some other hormones. The electrolyte content in plasma is basically the same as that in tissue fluid.

(2) Blood cells

During the life of the body, blood cells are constantly metabolizing. The average life span of red blood cells is about 120 days, and the life span of granular white blood cells and platelets generally does not exceed 10 days. The life span of lymphocytes varies from a few hours to several years.

Blood cells and platelets are produced from hematopoietic organs. Red blood cells, granular white blood cells and platelets are produced by red bone marrow, while agranulocytes are produced by lymph nodes and spleen.

There are three types of blood cells: red blood cells, white blood cells, and platelets.

An adult has about 5 liters of blood. By volume, blood cells account for about 45% of blood. Each liter of blood has:

5x1012 Red blood cells (about 45% of blood volume): In mammals, mature red blood cells have no nucleus and organelles. They have heme to transport oxygen. The glycoprotein on the red blood cell determines the blood type. The proportion of red blood cells in the blood is called hematocrit. The total surface area of ​​all red blood cells in the human body is approximately 2000 times the area of the skin outside the body.

9x1011 White blood cells (about 1.0% of blood volume): They are part of the immune system, responsible for destroying and removing old or abnormal cells and cell debris, and attacking pathogens and foreign objects.

3x1011 Platelets (approximately less than 1% of the blood volume): They are responsible for blood clotting, turning fibrinogen into fibrin. Fibrin forms a network to gather red blood cells to form a thrombus, which prevents more blood loss and helps prevent bacteria from entering the body.

What is plasma?

Plasma definition: Plasma refers to the liquid part of the whole blood after separation. It is based on a solution of crystalline substances, including water and a variety of electrolytes, as well as small molecules of organic matter and gases dissolved in it.

Classification of plasma

  1. Fresh plasma: Contains normal amounts of all coagulation factors. It is suitable for patients with coagulation factor deficiency.
  2. Preserved plasma: Suitable for patients with low blood volume and low plasma protein.
  3. Frozen plasma: Ordinary frozen plasma is stored at low temperature ~ 30℃ and is valid for 1 year. Melt in 37℃ warm water before application.
  4. Fresh frozen plasma: In the United States, it refers to the fluid portion of one unit of whole blood that has been centrifuged, separated, and frozen solid at −18 °C (0 °F) or colder within eighthours of collection from whole blood donation or was otherwise collected via apheresis device.
  5. Dried plasma: appropriate amount of 0.9% sodium chloride solution or 0.1% sodium citrate solution can be added for dissolution.

Appearance

Plasma is equivalent to the intercellular stroma of connective tissue. Plasma has a pale yellowcolor because it contains bilirubin. Water makes up 90 to 92 percent of the chemical composition of the plasma, with the other 10 percent in the form of solutes in proteins, nutrients, hormones, cholesterol, and other important substances.

 Function

Carry blood cells, transport substances needed to maintain the body and producing waste, etc.

How is plasma donated?

 Plasma donation is one of the methods of component blood donation. The technology of plasma donation is to extract the human blood from the body, separate it in the automatic machine, and return red blood cells to the donor. Only the plasma part is collected. The whole process uses disposable consumables and is completed in completely enclosed environment. Plasma donation is one of best way to treat the novel coronavirus for it includes antibody of SARS-CoV-2. How to donate plasma? Should consult the local authority department.  

How do you increase plasma in your body?

  1. Drink vitamin or iron supplements: Sometimes vitamin C helps the body absorb iron. Low levels of vitamin or iron in the body can cause certain types of anemia.
  2. Change your diet: It is recommended to eat more red meat, especially beef or liver, and chicken, pork, fish and shellfish are also rich in iron and can be used as a salubrious diet to treat anemia.
  3. Drugs: With too little blood in your body, your doctor may help prescribe drugs to help your body produce more red blood cells.

What is serum?

Serum definition: Blood serum refers to the gelatinous fluid in plasma after fibrinogen is removed.

Components

It is mainly composed of water and various chemical components, such as albumin, α1、α2、β、γ-globulin, triglyceride, total cholesterol, alanine aminotransferase and so on. Serum contains a variety of plasma proteins, peptides, fats, carbohydrates, growth factors, hormones, inorganic substances, and so on. These substances promote cell growth or inhibit growth activity so as to achieve physiological balance.

What does a serum do?

  1. Provide essential nutrients: amino acids, vitamins, inorganic substances, lipids, nucleic acid derivatives, etc.
  2. Provides hormones and various growth factors
  3. Provide binding proteins: Binding proteins act as carriers of important low molecular weight substances
  4. Provides contact - promoting and extension factors to protect cells from mechanical damage
  5. It has some protective effect on cultured cells.

What is the difference between serum and plasma?

Serum vs Plasma

difference between serum and plasma
difference between serum and plasma
  1. Definition: The answer is given above.
  2. Relationship: As defined above, serum is contained in plasma.
  3. Color:
    1. The plasma is the remaining part of the whole blood after the separation of bleeding cells, which is pale yellow.
    2. Serum refers to the clear liquid precipitated on the surface of the blood clot after the coagulation of plasma, which is light yellow and transparent.
  4. Density: Plasma contains a variety of coagulation factors, so its density is higher than the serum.
  5. Composition: The biggest difference is the absence of fibrinogen in the serum.
  6. Coagulation: The addition of calcium ions to plasma causes it to solidify, while it can’t do it to serum.
  7. Clotting factors: Plasma contains clotting agents. While serum is a watery fluid in the blood without clotting factors.
  8. Water content: Plasma contains 92-95% water. While 90% of the serum is water.
  9. Components: Plasma contains clotting factors and water. Serum contains albumin and globulin and other proteins.
  10. rrangement: The cells are not attached and are suspended in plasma. While for serum, cells usually stick together through the formation of blood clots.
  11. Separation: Plasma is acquired from the spinning before clotting.
    While serum is obtained from the spinning after clotting.
  12. Function: Plasma is mainly applied to the detection of coagulation, and serum is mainly used for the detection of blood biochemistry, immunity and other aspects.
  13. Anticoagulants: Anticoagulants are needed to obtain plasma. While anticoagulants are not required for the separation of serum.
  14. Feasibility of separation: Plasma separation is relatively easier and cheaper.
  15. The amount of blood: Plasma accounts for 55% of the total blood. Serum has a smaller portion.
  16. Storage: Frozen plasma can be stored for up to one year. Serum can be stored at 2-6 degrees (Celsius) for just several days.
  17. Discoloration: Plasma shows an inclination to discolor when standing, and serum does not.
  18. Significance: The function of plasma is the excretion of metabolites and transport of substances in the blood. It also helps maintain blood pressure and regulate body temperature. While serum is a major source of electrolytes.

FAQ

1. Why serum is used instead of plasma?

Situations in which serum rather than plasma is commonly used:

2. Are antibodies is plasma or serum?  

Antibodies exist in serum, lymph, mucosal secretions and tissues, but with the highest content in serum. And antibodies are often obtained by the separation of the serum, so antibodies are also called anti-serum.

3. What is plasma membrane function?

There is no relevance between plasma membrane and plasma.
Plasma membrane was used to be called “cell membrane”, which is a very thin membrane that surrounds the cell surface and is mainly composed of membrane lipids and membrane proteins.

The basic role of the plasma membrane is to maintain the relative stability of the intracellular microenvironment and to participate in the material exchange with the external environment. In addition, it plays a crucial part in the survival, growth, division and differentiation of cells.

Conclusion

Serum vs plasma: The difference between them is clearly shown in above information, which can help design IVD product while doing lateral flow assay development in in-vitro diagnostics.

References