Antibodies (immunoglobulins, Ig, Ig) is a special class of glycoproteins present on the surface of B cells in the form of membrane-bound receptors and in serum and tissue fluid in the form of soluble molecules. They are the most important factor in specific humoral immunity. Antibodies are used by the immune system to identify and neutralize foreign objects such as bacteria and viruses. Antibodies have two functions: antigen-binding and effector (cause one or another immune response, for example, trigger the classical scheme of complement activation).
Antibodies are synthesized by plasma cells, which become B-lymphocytes in response to the presence of antigens. For each antigen, specialized plasma cells corresponding to it are formed, producing antibodies specific for this antigen. Antibodies recognize antigens by binding to a specific epitope - a characteristic fragment of the surface or linear amino acid chain of an antigen.
Antibodies are composed of two light chains and two heavy chains. In mammals, five classes of antibodies (immunoglobulins) are distinguished - IgG, IgA, IgM, IgD, IgE, differing from each other in the structure and amino acid composition of heavy chains and in the effector functions performed.
Study history
The very first antibody was discovered by Bering and Kitazato in 1890 year, however, at this time about the nature of the discovered tetanus antitoxin apart from its specificity and its presence in serum immune animal, nothing definite could be said. Only with 1937 year- research by Tiselius and Kabat, the study of the molecular nature of antibodies begins. The authors used the method electrophoresis proteins and demonstrated an increase in the gamma-globulin fraction of the blood serum of immunized animals. Adsorption serum antigen, which was taken for immunization, reduced the amount of protein in this fraction to the level of intact animals.
Antibody structure
General plan of the structure of immunoglobulins: 1) Fab; 2) Fc; 3) heavy chain; 4) light chain; 5) antigen-binding site; 6) hinge section
Antibodies are relatively large (~ 150 k Yes- IgG) glycoproteins having a complex structure. Consist of two identical heavy chains(H-chains, in turn consisting of V H, C H1, hinge, C H2 and C H3 domains) and two identical light chains(L-chains consisting of V L and C L domains). Oligosaccharides are covalently attached to heavy chains. With protease papain antibodies can be split into two Fab (English fragment antigen binding- antigen-binding fragment) and one Fc (English fragment crystallizable- a fragment capable of crystallization). Depending on the class and the functions performed, antibodies can exist both in monomeric form (IgG, IgD, IgE, serum IgA) and in oligomeric form (dimer-secretory IgA, pentamer - IgM). In total, there are five types of heavy chains (α-, γ-, δ-, ε- and μ-chains) and two types of light chains (κ-chain and λ-chain).
Heavy chain classification
There are five classes ( isotypes) immunoglobulins, differing:
amino acid sequence
size
IgG class is classified into four subclasses (IgG1, IgG2, IgG3, IgG4), IgA class - into two subclasses (IgA1, IgA2). All classes and subclasses constitute nine isotypes that are normally present in all individuals. Each isotype is defined by the amino acid sequence of the heavy chain constant region.
Antibody functions
Immunoglobulins of all isotypes are bifunctional. This means that any type of immunoglobulin
recognizes and binds the antigen, and then
enhances killing and / or removal of immune complexes formed as a result of the activation of effector mechanisms.
One region of the antibody molecule (Fab) determines its antigenic specificity, while the other (Fc) performs effector functions: binding to receptors that are expressed on the cells of the body (for example, phagocytes); binding to the first component (C1q) of the complement system to initiate the classic pathway of the complement cascade.
IgG is the main immunoglobulin serum a healthy person (makes up 70-75% of the entire fraction of immunoglobulins), is most active in the secondary immune response and antitoxic immunity. Due to its small size ( sedimentation coefficient 7S, molecular weight 146 kDa) is the only fraction of immunoglobulins capable of transport across the placental barrier and thereby providing immunity to the fetus and newborn. As part of IgG 2-3% carbohydrates; two antigen-binding F ab -fragments and one F C -fragment. F ab -fragment (50-52 kDa) consists of the whole L-chain and the N-terminal half of the H-chain, connected to each other disulfide bond, while the F C -fragment (48 kDa) is formed by the C-terminal halves of the H-chains. There are 12 domains in the IgG molecule (regions formed from β-structures and α-helices Ig polypeptide chains in the form of disordered formations linked by disulfide bridges of amino acid residues within each chain): 4 for heavy and 2 for light chains.
IgM are a pentamer of the basic four-stranded unit containing two μ-chains. Moreover, each pentamer contains one copy of a J-chain polypeptide (20 kDa), which is synthesized by an antibody-producing cell and covalently binds between two adjacent F C fragments of immunoglobulin. They appear during the primary immune response by B-lymphocytes to an unknown antigen, and account for up to 10% of the immunoglobulin fraction. They are the largest immunoglobulins (970 kDa). Contains 10-12% carbohydrates. The formation of IgM occurs even in pre-B-lymphocytes, in which they are primarily synthesized from the μ-chain; the synthesis of light chains in pre-B cells ensures their binding to μ-chains, as a result, functionally active IgM are formed, which are incorporated into the surface structures of the plasma membrane, acting as an antigen-recognizing receptor; from this moment, the cells of the pre-B-lymphocytes become mature and are able to participate in the immune response.
IgA serum IgA makes up 15-20% of the total fraction of immunoglobulins, while 80% of IgA molecules are present in monomeric form in humans. Secretory IgA is presented in dimeric form in a complex secretory component contained in serous-mucous secretions (for example, in saliva, tears, colostrum, milk separated by the mucous membrane of the genitourinary and respiratory system). Contains 10-12% carbohydrates, molecular weight 500 kDa.
IgD makes up less than one percent of the plasma immunoglobulin fraction, is found mainly on the membrane of some B-lymphocytes. Functions not fully understood, presumably an antigen receptor with a high content of protein-bound carbohydrates for B-lymphocytes, not yet presented to the antigen. Molecular mass 175 kDa.
Antigen classification
so called "Antibodies-bystanders of the disease", the presence of which in the body signals the acquaintance of the immune system with this pathogen in the past or current infection with this pathogen, but which do not play a significant role in the body's fight against the pathogen (they do not neutralize either the pathogen itself or its toxins, but bind to minor proteins of the pathogen ).
autoaggressive antibodies, or autologous antibodies, autoantibodies- antibodies that cause destruction or damage to normal, healthy tissue itself organism host and triggering the development mechanism autoimmune diseases.
alloreactive antibodies, or homologous antibodies, alloantibodies- antibodies against antigens of tissues or cells of other organisms of the same biological species. Alloantibodies play an important role in the processes of rejection of allografts, for example, during transplantation kidneys, liver, bone marrow, and in reactions to transfusion of incompatible blood.
heterologous antibodies, or isoantibodies- antibodies against antigens of tissues or cells of organisms of other biological species. Isoantibodies are the reason for the impossibility of xenotransplantation even between evolutionarily close species (for example, chimpanzee liver transplantation to humans is impossible) or species with similar immunological and antigenic characteristics (pig organ transplantation to humans is impossible).
anti-idiotypic antibodies - antibodies against antibodies produced by the body itself. Moreover, these antibodies are not "in general" against the molecule of this antibody, namely against the working, "recognizing" section of the antibody, the so-called idiotype. Anti-idiotypic antibodies play an important role in binding and neutralizing excess antibodies, in the immune regulation of antibody production. In addition, the anti-idiotypic “antibody against antibody” mirrors the spatial configuration of the parent antigen against which the parent antibody was generated. And thus, the anti-idiotypic antibody serves as a factor of immunological memory for the body, an analogue of the original antigen, which remains in the body even after the destruction of the original antigens. In turn, anti-idiotypic antibodies can be produced anti-anti-idiotypic antibodies, etc.
Antibody specificity
Means that everyone lymphocyte synthesizes antibodies of only one specific specificity. And these antibodies are located on the surface of this lymphocyte as receptors.
Experiments show that all surface immunoglobulins of a cell have the same idiotype: when soluble antigen like polymerized flagellin, binds to a specific cell, then all cell surface immunoglobulins bind to this antigen and they have the same specificity, that is, the same idiotype.
The antigen binds to receptors, then selectively activates the cell to form a large number antibodies. And since cell synthesizes antibodies of only one specificity, then this specificity should match the specificity of the initial surface receptor.
The specificity of the interaction of antibodies with antigens is not absolute; they can, to varying degrees, cross-react with other antigens. Antiserum obtained to one antigen can react with a related antigen carrying one or more of the same or similar determinant... Therefore, each antibody can react not only with the antigen that caused its formation, but also with other, sometimes completely unrelated molecules. The specificity of antibodies is determined by the amino acid sequence of their variable regions.
Clonal breeding theory:
Antibodies and lymphocytes with the desired specificity already exist in the body before the first contact with the antigen.
Lymphocytes, which are involved in the immune response, have antigen-specific receptors on the surface of their membrane. Have B-lymphocytes receptors are molecules of the same specificity as antibodies that lymphocytes subsequently produce and secrete.
Any lymphocyte carries receptors of only one specificity on its surface.
Lymphocytes having antigen, go through the stage proliferation and form a large clone of plasma cells. Plasma cells they synthesize antibodies only of the specificity for which the precursor lymphocyte has been programmed. Proliferation signals are cytokines that are secreted by other cells. Lymphocytes can secrete cytokines themselves.
Antibody variability
Antibodies are extremely variable (up to 10 8 variants of antibodies can exist in the body of one person). All the diversity of antibodies stems from the variability of both heavy chains and light chains. The antibodies produced by this or that organism in response to certain antigens are distinguished:
Isotypic variability - manifested in the presence of classes of antibodies (isotypes), differing in the structure of heavy chains and oligomericity, produced by all organisms of a given species;
Allotypical variability - manifested at the individual level within a given species in the form of variability of alleles of immunoglobulins - is a genetically determined difference of a given organism from another;
Idiotypical variability - manifested in the difference in the amino acid composition of the antigen-binding site. This concerns the variable and hypervariable domains of the heavy and light chains in direct contact with the antigen.
Control of proliferation
The most effective control mechanism is that the reaction product simultaneously serves its inhibitor... This type of negative feedback occurs in antibody production. The action of antibodies cannot be explained simply by neutralizing the antigen, because whole IgG molecules suppress antibody synthesis much more efficiently than F (ab ") 2 fragments. , IgG and Fc - receptors on the surface of B cells. Injection IgM, enhances immune response... Since antibodies of this particular isotype appear first after the introduction of the antigen, they are attributed to an enhancing role at an early stage of the immune response.
Table of contents of the subject "Humoral immune reactions. The main types of antibodies. The dynamics of antibody formation.":Antibodies (AT) are usually classified according to the type of their reactions with Ar.
Antitoxic antibodies(AT) to toxins and toxoids neutralize or flocculate Ag.
Agglutinating antibodies(AT) aggregate Ag. They are detected in reactions with corpuscular Ar and soluble Ar sorbed on the surface of visible particles (erythrocytes, latex particles).
Precipitating antibodies(AT) form a complex of Ag-AT with soluble Ag only in solutions or gels.
Lyse antibodies(AT) cause destruction of target cells (usually by interacting with complement).
Opsonizing antibodies(AT) interact with the surface structures of microbial cells or infected cells of the body, promoting their absorption by phagocytes.
Neutralizing antibodies(AT) inactivate Ag (toxins, microorganisms), depriving them of the opportunity to exhibit a pathogenic effect.
The main functions of antibodies (AT)
Antibodies (AT) through Ar-binding centers interact with various Ar. Thus, ATs prevent infection or eliminate the pathogen, or block the development of pathological reactions, while activating all systems of specific defense.
Opsonization (immune phagocytosis). Antibodies(AT) (via Fab-fragments) bind to the labeling wall of the microorganism: the AT Fc-fragment interacts with the corresponding phagocyte receptor. This mediates the subsequent effective absorption of the formed complex by the phagocyte.
Antitoxic effect. Antibodies(AT) can bind and thereby inactivate bacterial toxins.
Complement activation. Antibodies(AT) (IgM and IgG), after binding to Ag (microorganism, tumor cell, etc.), activate the complement system, which leads to the destruction of this cell by perforating its cell wall, enhancing chemotaxis, chemokinesis, and immune phagocytosis.
Neutralization... By interacting with cell receptors that bind bacteria or viruses, AT can prevent the adhesion and penetration of microorganisms into the cells of the host organism.
Circulating immune complexes. Antibodies(AT) bind soluble Ag and form circulating complexes, with the help of which Ag is excreted from the body, mainly with urine and bile.
Antibody dependent cytotoxicity... Opsonizing Ag, antibodies(AT) stimulate their destruction by cytotoxic cells. The target recognition apparatus is the receptors for the Fc fragments of AT. Macrophages and granulocytes (for example, neutrophils) are capable of destroying opsonized targets.
Binding and effector (they cause one or another immune response, for example, they start the classical scheme of complement activation).
Antibodies are synthesized by plasma cells, which become some B-lymphocytes, in response to the presence of antigens. For each antigen, specialized plasma cells corresponding to it are formed, producing antibodies specific for this antigen. Antibodies recognize antigens by binding to a specific epitope - a characteristic fragment of the surface or linear amino acid chain of an antigen.
Antibodies are composed of two light and two heavy chains. In mammals, five classes of antibodies (immunoglobulins) are distinguished - IgG, IgA, IgM, IgD, IgE, differing from each other in the structure and amino acid composition of heavy chains and in the effector functions performed.
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The very first antibody was discovered by Bering and Kitazato in 1890, but at that time nothing definite could be said about the nature of the tetanus antitoxin discovered, other than its specificity and its presence in the serum of an immune animal. Only in 1937 - studies of Tiselius and Kabat - began to study the molecular nature of antibodies. The authors used the method of protein electrophoresis and demonstrated an increase in the gamma-globulin fraction of the blood serum of immunized animals. Serum adsorption by the antigen taken for immunization reduced the amount of protein in this fraction to the level of intact animals.
Antibody structure
Antibodies are relatively large (~ 150 kDa - IgG) glycoproteins with a complex structure. They consist of two identical heavy chains (H-chains, in turn consisting of VH, C H 1, a hinge, CH 2- and CH 3-domains) and two identical light chains (L-chains consisting of VL - and CL - domains). Oligosaccharides are covalently attached to heavy chains. With the help of papain protease, antibodies can be cleaved into two Fab (fragment antigen binding) and one (fragment crystallizable). Depending on the class and the functions they perform, antibodies can exist both in monomeric form (IgG, IgD, IgE, serum IgA) and in oligomeric form (dimer-secretory IgA, pentamer - IgM). In total, there are five types of heavy chains (α-, γ-, δ-, ε- and μ-chains) and two types of light chains (κ-chain and λ-chain).
Heavy chain classification
There are five classes ( isotypes) immunoglobulins, differing:
- amino acid sequence
- molecular weight
- charge
The IgG class is classified into four subclasses (IgG1, IgG2, IgG3, IgG4), the IgA class into two subclasses (IgA1, IgA2). All classes and subclasses constitute nine isotypes that are normally present in all individuals. Each isotype is defined by the amino acid sequence of the heavy chain constant region.
Antibody functions
Immunoglobulins of all isotypes are bifunctional. This means that any type of immunoglobulin
- recognizes and binds the antigen, and then
- enhances the destruction and / or removal of immune complexes formed as a result of the activation of effector mechanisms.
One region of the antibody molecule (Fab) determines its antigenic specificity, while the other (Fc) performs effector functions: binding to receptors that are expressed on body cells (for example, phagocytes); binding to the first component (C1q) of the complement system to initiate the classic pathway of the complement cascade.
Means that each lymphocyte synthesizes antibodies of only one specific specificity. And these antibodies are located on the surface of this lymphocyte as receptors.
Experiments show that all surface immunoglobulins of a cell have the same idiotype: when a soluble antigen, similar to polymerized flagellin, binds to a specific cell, then all cell surface immunoglobulins bind to this antigen and they have the same specificity, that is, the same idiotype.
The antigen binds to receptors, then selectively activates the cell with the formation of a large number of antibodies. And since the cell synthesizes antibodies of only one specificity, this specificity must coincide with the specificity of the initial surface receptor.
The specificity of the interaction of antibodies with antigens is not absolute; they can, to varying degrees, cross-react with other antigens. Antisera raised to a single antigen can react with a related antigen carrying one or more of the same or similar determinants. Therefore, each antibody can react not only with the antigen that caused its formation, but also with other, sometimes completely unrelated molecules. The specificity of antibodies is determined by the amino acid sequence of their variable regions.
Clonal breeding theory:
- Antibodies and lymphocytes with the desired specificity already exist in the body before the first contact with the antigen.
- Lymphocytes, which are involved in the immune response, have antigen-specific receptors on the surface of their membrane. In B-lymphocytes, receptors are molecules of the same specificity as antibodies, which lymphocytes subsequently produce and secrete.
- Any lymphocyte carries receptors of only one specificity on its surface.
- Lymphocytes with antigen go through the stage of proliferation and form a large clone of plasma cells. Plasma cells synthesize antibodies only of the specificity for which the precursor lymphocyte has been programmed. The signals for proliferation are cytokines secreted by other cells. Lymphocytes can secrete cytokines themselves.
Antibody variability
Antibodies are extremely variable (up to 10 8 variants of antibodies can exist in the body of one person). All the diversity of antibodies stems from the variability of both heavy chains and light chains. The antibodies produced by this or that organism in response to certain antigens are distinguished:
- Isotypic variability - manifested in the presence of classes of antibodies (isotypes), differing in the structure of heavy chains and oligomericity, produced by all organisms of a given species;
- Allotypical variability - manifested at the individual level within a given species in the form of variability of alleles of immunoglobulins - is a genetically determined difference of a given organism from another;
- Idiotypical variability - manifested in the difference in the amino acid composition of the antigen-binding site. This concerns the variable and hypervariable domains of the heavy and light chains in direct contact with the antigen.
Control of proliferation
The most effective control mechanism is that the reaction product simultaneously serves as its inhibitor. This type of negative feedback occurs in antibody production. The action of antibodies cannot be explained simply by neutralizing the antigen, because whole IgG molecules suppress antibody synthesis much more efficiently than F (ab ") 2 fragments. , IgG and Fc - receptors on the surface of B-cells. Injection of IgM enhances the immune response. Since antibodies of this particular isotype appear first after the introduction of the antigen, they are attributed to an enhancing role at an early stage of the immune response.
Antibodies (immunoglobulins, Ig, Ig) are a special class of glycoproteins present on the surface of B-lymphocytes in the form of membrane-bound receptors and in serum and tissue fluid in the form of soluble molecules, and having the ability to very selectively bind to specific types of molecules, which, due to these are called antigens. Antibodies are the most important factor in specific humoral immunity. Antibodies are used by the immune system to identify and neutralize foreign objects such as bacteria and viruses. Antibodies perform two functions: antigen-binding and effector (they cause one or another immune response, for example, they trigger the classical scheme of complement activation).
Antibodies are synthesized by plasma cells, which become some B-lymphocytes, in response to the presence of antigens. For each antigen, specialized plasma cells corresponding to it are formed, producing antibodies specific for this antigen. Antibodies recognize antigens by binding to a specific epitope - a characteristic fragment of the surface or linear amino acid chain of an antigen.
Antibodies are proteins of a globulin nature (immunoglobulins) that are formed in the body under the influence of an antigen and have the ability to selectively bind to it. There are five types of molecules (classes) of immunoglobulins with a molecular weight of 150 to 900 thousand daltons: IgM, lgG, IgA, IgE, IgD. Immunoglobulin molecules consist of two light (L) and two heavy (H) polypeptide chains interconnected by disulfide bonds. Both types of chains connected to each other are antigenic. In heavy chains, it is specific for each class of immunoglobulins and, accordingly, the classes of H-chains are designated m, g, a, e, s. Antigenically, light chains are divided into two types - X and l, which are the same for different classes. Antigenic differences in heavy chains are used to obtain antisera, which can reveal the presence of immunoglobulins of one class or another in the test material. IgG light chains consist of two regions (domains): variable (VL) and constant (CL). Heavy chains include one variable (V H) and 3 constant regions (CH 1, CH 2, CH 3). The variable regions of the light and heavy chains form the active sites of antibodies (VL-VH). The CL - CH 1 region defines small differences in the sequence of amino acids in individuals of the same species (alloantigenic differences in IgM molecules). The CH 2 -CH 2 region is involved in the fixation and activation of complement, and the CH 3 -CH 3 region is involved in the fixation of antibodies to cells (lymphocytes, macrophages, mast cells). This type of molecular structure is also characteristic of all other classes of immunoglobulins, the differences lie in the additional organization of this basic unit. Thus, the IgM H-chain consists not of 4, but of 5 domains, and the entire IgM molecule is a pentamer of an IgG molecule connected by additional polypeptide J-chains. IgA can be in the form of monomers, dimers and secretory IgA. The latter two forms have additional (dimers) J or J and S chains (secretory). Other properties of antibodies are presented in table 5.
Table 5.
Main characteristics of human immunoglobulins
Indicators
Molecular mass
170t. and 300t.
Blood level in g / l
Heavy chain type
Fixation C
Neutralization of toxins
Agglutination
Bacteriolysis
Passage of the placenta
The antibody molecule does not bind to the antigen determinant entirely, but only to a certain part of it, called the active center. The active center is a cavity or gap corresponding to the spatial configuration of the antigen determinant group. One of the active centers can be functionally inert for various reasons. These antibodies are called incomplete antibodies. Their appearance is usually preceded by the formation of complete, i.e., antibodies with two (IgG) active centers. Incomplete antibodies are found in different classes of immunoglobulins. The bulk of antibodies is formed in cells of the plasmacytic series (plasmablast, proplasmacyte, plasmacyte). Each of them produces antibodies of only one specificity, that is, to one antigenic determinant. Geographically, these cells are located in the spleen, lymph nodes, bone marrow, lymphoid formations of the mucous membranes. At the initial contact of the body with the antigen and antibody formation, inductive and productive phases are distinguished. The duration of the first phase is about 2 days. During this period, the proliferation and differentiation of lymphoid cells occurs, the development of a plasmablastic reaction. Following the inductive phase comes the productive phase. In the blood serum, antibodies begin to be determined from the 3rd day after contact with the antigen. These antibodies belong to the IgM class. From 5-7 days, there is a gradual change from IgM synthesis to IgG synthesis of the same specificity. Usually, by 12-15 days, the curve of antibody production reaches its maximum, then the level of antibodies begins to decline, but a certain amount of them can be detected even after many months, and sometimes years. With repeated contact of the body with the same antigen, the inductive phase takes only a few hours. The productive phase proceeds faster and more intensively, mainly IgG is synthesized.
Immunoglobulins of all isotypes are bifunctional. This means that any type of immunoglobulin recognizes and binds the antigen, and then enhances the killing and / or removal of immune complexes formed as a result of the activation of effector mechanisms.
One region of the antibody molecule (Fab) determines its antigenic specificity, while the other (Fc) performs effector functions: binding to receptors that are expressed on body cells (for example, phagocytes); binding to the first component (C1q) of the complement system to initiate the classic pathway of the complement cascade.
IgG is the main immunoglobulin serum a healthy person (makes up 70-75% of the entire fraction of immunoglobulins), is most active in the secondary immune response and antitoxic immunity. Due to its small size ( sedimentation coefficient 7S, molecular weight 146 kDa) is the only fraction of immunoglobulins capable of transport across the placental barrier and thereby providing immunity to the fetus and newborn. As part of IgG 2-3% carbohydrates; two antigen-binding F ab -fragments and one F C -fragment. F ab -fragment (50-52 kDa) consists of the whole L-chain and the N-terminal half of the H-chain, connected to each other disulfide bond, while the F C -fragment (48 kDa) is formed by the C-terminal halves of the H-chains. There are 12 domains in the IgG molecule (regions formed from β-structures and α-helices Ig polypeptide chains in the form of disordered formations linked by disulfide bridges of amino acid residues within each chain): 4 for heavy and 2 for light chains.
IgM are a pentamer of a basic four-chain unit containing two μ-chains. Moreover, each pentamer contains one copy of a J-chain polypeptide (20 kDa), which is synthesized by an antibody-producing cell and covalently binds between two adjacent F C fragments of immunoglobulin. They appear during the primary immune response by B-lymphocytes to an unknown antigen, and account for up to 10% of the immunoglobulin fraction. They are the largest immunoglobulins (970 kDa). Contains 10-12% carbohydrates. The formation of IgM occurs even in pre-B-lymphocytes, in which they are primarily synthesized from the μ-chain; the synthesis of light chains in pre-B cells ensures their binding to μ-chains, as a result, functionally active IgM are formed, which are incorporated into the surface structures of the plasma membrane, acting as an antigen-recognizing receptor; from this moment, the cells of the pre-B-lymphocytes become mature and are able to participate in the immune response.
Serum IgA IgA makes up 15-20% of the total fraction of immunoglobulins, while 80% of IgA molecules are present in monomeric form in humans. The main function of IgA is to protect the mucous membranes of the respiratory, urinary tract and gastrointestinal tract from infections. Secretory IgA is presented in dimeric form in a complex secretory component contained in serous-mucous secretions (for example, in saliva, tears, colostrum, milk separated by the mucous membrane of the genitourinary and respiratory system). Contains 10-12% carbohydrates, molecular weight 500 kDa.
IgD makes up less than one percent of the plasma immunoglobulin fraction, and is found mainly on the membrane of some B-lymphocytes. Functions not fully understood, presumably an antigen receptor with a high content of protein-bound carbohydrates for B-lymphocytes, not yet presented to the antigen... Molecular weight 175 kDa.
Antigen classification
the so-called "antibodies-witnesses of the disease", the presence of which in the body signals the acquaintance of the immune system with this pathogen in the past or current infection with this pathogen, but which do not play a significant role in the body's fight against the pathogen (they do not neutralize either the pathogen itself or its toxins, but bind to minor proteins of the pathogen).
autoaggressiveantibodies, or autologous antibodies, autoantibodies - antibodies that cause destruction or damage to normal, healthy tissue itself organism host and triggering the development mechanism autoimmune diseases.
alloreactive antibodies, or homologous antibodies, alloantibodies - antibodies against antigens of tissues or cells of other organisms of the same biological species. Alloantibodies play an important role in the processes of rejection of allografts, for example, during transplantation kidneys, liver, bone marrow, and in reactions to transfusion of incompatible blood.
heterologous antibodies, or isoantibodies - antibodies against antigens of tissues or cells of organisms of other biological species. Isoantibodies are the reason for the impossibility of xenotransplantation even between evolutionarily close species (for example, chimpanzee liver transplantation to humans is impossible) or species with similar immunological and antigenic characteristics (pig organ transplantation to humans is impossible).
anti-idiotypic antibodies - antibodies against antibodies produced by the body itself. Moreover, these antibodies are not "in general" against the molecule of this antibody, namely against the working, "recognizing" section of the antibody, the so-called idiotype. Anti-idiotypic antibodies play an important role in binding and neutralizing excess antibodies, in the immune regulation of antibody production. In addition, the anti-idiotypic “antibody against antibody” mirrors the spatial configuration of the parent antigen against which the parent antibody was generated. And thus, the anti-idiotypic antibody serves as a factor of immunological memory for the body, an analogue of the original antigen, which remains in the body even after the destruction of the original antigens. In turn, anti-idiotypic antibodies, etc., can be produced against anti-idiotypic antibodies.
Monoclonal antibodies - antibodies generated by immune cells belonging to the same cellular clone, that is, originated from one plasma progenitor cell... Monoclonal antibodies can be raised against almost any natural antigen (mainly proteins and polysaccharides), which the antibody will specifically bind. They can then be used to detect (detect) this substance or purify it.
Hybridoma - a hybrid cell artificially obtained on the basis of fusion of an antibody-producing B-lymphocyte with a cancer cell, which gives this hybrid cell the ability to multiply unrestrictedly during cultivation in vitro, which carries out the synthesis of specific immunoglobulins of one isotype - monoclonal antibodies. Hybridomas producing monoclonal antibodies are propagated either in apparatus adapted for growing cell cultures or by injecting them intraperitoneally of a special line (ascites) mice. In the latter case, monoclonal antibodies accumulate in the ascites fluid, in which hybridomas multiply. Monoclonal antibodies obtained by either method are purified, standardized and used to create diagnostic preparations based on them. Hybridoma monoclonal antibodies have found wide application in the development of diagnostic and therapeutic immunobiological preparations.
One of the fractions of blood proteins (gamma globulins), which is synthesized by lymphocytes for a specific connection with molecules foreign to the body (antigens). The appearance of foreign antigens induces the synthesis of antibodies and the start of the immune defense mechanism. Physical anthropology
- antibodies - ANTIBODIES, immunoglobulins of different classes, formed in the body under the influence of antigen and having a specificity. affinity for him. Veterinary encyclopedic dictionary
- antibodies - Deep-seated proteins that have the ability to specifically bind to antigens. See immunoglobulins, antigen-antibody response. Biological encyclopedic dictionary
- antibodies - Substances formed in the body when introduced into it by injecting various foreign proteins (antigens) and neutralizing their harmful effects Large dictionary of foreign words
- antibodies - Anti / tel / a′. Morphemic-spelling dictionary
- antibodies - orph. antibodies, - bodies, units -body, -a Spelling dictionary Lopatin
- antibodies - -body, pl. (unit antibody, -a, cf.). biochem. Substances produced by the body when foreign substances are introduced into it and neutralizing their harmful effects. Small academic dictionary
- antibodies - Proteins of the immunoglobulin group formed in the human body and warm-blooded animals in response to the ingress of substances (antigens) into it and neutralizing their harmful effects. The main forms of manifestation of activity ... Microbiology. Glossary of terms
- ANTIBODIES - ANTIBODIES - globular proteins (immuno-globulins) of blood plasma of humans and warm-blooded animals, which have the ability to specifically bind to antigens. Big encyclopedic dictionary
- Antibodies - Proteins of the globulin fraction of blood serum formed in response to the introduction of bacteria, viruses, protein toxins and other antigens into the human body or warm-blooded animals (See Antigens). Great Soviet Encyclopedia
- antibodies - Specific proteins (immunoglobulins) formed by plasma cells (descendants of B-lymphocytes) in humans and animals when antigens are ingested. Exercise specific humoral immunity. Biology. Modern encyclopedia
- antibodies - ANTIBODIES - bodies; pl. (unit antibody, -a; cf.). Proteins produced by the human body or warm-blooded animal when foreign substances and microorganisms (antigens) enter it, neutralizing their harmful effect. Dictionary Kuznetsova
- antibodies - antibodies pl. Substances formed in the human or animal body when antigens enter it - foreign proteins, bacteria, etc. - and capable of neutralizing their harmful effects. Efremova's Explanatory Dictionary
- antibodies - ANTIBODIES, globular proteins capable of specifically binding to antigens. Formed in the body w-nogo plasmatic. cells in response to the penetration of antigens (microorganisms and their toxins, helminths, etc.). Agricultural Dictionary
- antibodies - ANTIBODIES, ate, units. antibody, a, cf. (specialist.). Complex proteins are substances that are formed in the body when foreign substances are introduced into it and neutralize their harmful effects. Ozhegov's Explanatory Dictionary