Antibodies specific gamma globulin in the blood serum, formed in response to the introduction of antigens or by natural contact of the body with substances antigenic nature (bacteria, toxins, proteins of different origin, polysaccharides, polysaccharide-protein complexes and others). To generate a significant amount of antibodies enough the ingestion of small amounts of antigen.
Antibodies play a significant role in the formation of immunity of the organism to infectious diseases (see Immunity). Containing antibodies serum obtained from the immunized animals, widely used for the treatment and prevention of diseases (diphtheria, tetanus, gas gangrene, botulism). Detection of antibodies in the serum has diagnostic value when the number of infectious diseases (abdominal and curricular a fever, brucellosis and other).
The main feature of antibodies is their ability to interact specifically with the corresponding antigen. Physical properties of antigen determine the nature of the observed immunological reaction between the antibody and the antigen. On the basis of these features antibodies are divided into agglutinin, precipitin and lnini. Cm. also Agglutination, Precipitation.

Antibodies are proteins that appear in the animal or human body after exposure to some substances - antigens.
Antibodies specifically connected with those substances or substances with a similar chemical structure), which caused the appearance of antibodies. Sometimes detected in the blood of antibodies against antigens (see)in which animals or people did not immunotherapies ("normal" antibodies). The emergence of some "normal" A. you can explain invisible hit antigens in the body (microbes, nutritional factors, and so on).
Together with proteins, which are deprived of activity A., but similar chemical structure and antigenic specificity antibodies form a group of immunoglobulins. A significant amount of antibodies present in the blood serum; are they and other biological fluids (lymph, urine, cerebrospinal fluid, and others), as well as in the tissues.
The bulk of immunoglobulins is ' -globulins that people are divided into three classes: 1) үG, or igG; this class has mol. weight 160 000, during electrophoresis in alkaline buffer migrates most slowly, characterized by small content of carbohydrates; 2) a., or igA.;3tot the class has also mol. weight 160 000, marseul during electrophoresis between and V-globulins () - or β2A-globulin), contains a lot of carbohydrates; 3)m, or igM; this class has mol. weight of about 900 000; he migrates in the zone of beta - 2 or a-globulin, contains a lot of carbohydrates.
Antibodies same specificity can be present among immunoglobulins all three classes. During the primary immunization next antigens are formed m or a mixture m and үG, and when re - mainly үGA.
Molecule үG consists of 4 peptide chains: two "heavy" (the old name of the N or (A) (mol. weighing about 50 000 and two "lungs" (x,light wavelength, the old name L or) with mol. weighing about 20 000. The peptide chain is connected five disulfide bridges.
Each antibody molecule contains two active centre. Under the action of proteolytic enzyme papain a molecule breaks into three pieces: two monovalent active, antigenspecific (Fab) with mol. weight of 60 000 and one inactive crystallising fragment (Fc) with mol. weighing about 80 000.
The appearance of antibodies is associated with the synthesis of new protein molecules in cells of the lymphatic tissue. A. synthesized mainly in plasmatic
cells and partly in the lymphocytes in the spleen, lymph nodes, skin, lungs, bone marrow, and so on, the only Exception is the liver, where it is synthesized the bulk whey proteins, but not immunoglobulins.
After the introduction of antigen antibodies appear through some of the so-called latent period (from several days to 2-3 weeks). The introduction of the antigen causes immunological transformation, which resulted in the re-introduction of antigen adult animal usually accompanied by a more vigorous A. synthesis than the primary. In contrast, the introduction of the antigen to the embryo or newborn animal in many cases leads to loss of the ability to form antibodies in response to subsequent immunization same antigen (immunological tolerance).
Detection in serum of people or animals antibodies has diagnostic value and allows to judge about the causative agents. To detect A. use A. reaction to the antigen. The result of such a response outside the body produces sludge (precipitate), there is a coalescence of erythrocytes or bacteria (agglutination bacteria), dissolution of red blood cells and bacteria, neutralization of viruses and toxins, binding complement, etc.
In the interaction of antigen with antibodies in the body can occur in various pathological processes (anaphylaxis, serum sickness, and so on). Serum of people and animals (or a selection of them drugs - gamma-globulin, diapers and so on), containing A. against a number of diseases, are used to prevent and treat these diseases. Cm. also Immunity.