Antibodies are the body's defenses
Specific globulins formed by the bodyunder the action of an antigen, are called antibodies. Their special properties include the ability of the compound with the antigen that caused their formation, as well as the protection of the body from the effects of infectious agents. Antibodies are neutralizers of infectious agents, which reduce the susceptibility of the latter to the effects of complement or phagocytes.
There are two categories of antibodies:
- Precipitating, or complete. Their interaction with the antigen gives a visible immunological process, such as precipitation or agglutination reactions.
- Non-attributive, or incomplete. This is the category of blocking antibodies. They do not give a visible reaction at the time of the compound with the antigen.
The content of antibodies in human serum
Antibodies have a different effect on microorganisms: antitoxic, antimicrobial and anticellular. There are antibodies that neutralize viruses and immobilize spirochetes.
Differentiate antibodies to those that glue together erythrocytes (hemagglutinins), dissolve red blood cells (hemolysins) and kill animal cells (cytotoxins).
Against their own protein in the destruction of organs and tissues are autoantibodies. They are produced by releasing the antigen when the chemical structure of the organism changes.
Serum can detect circulatingantibodies. This is an antibody test performed on the basis of immunological reactions, such as complement fixation, precipitation, or agglutination. It shows both intracellular and cell-related forms.
Immunity. Functions of antibodies
The serum of a practically healthy person contains natural antibodies. These are the bodies that provide immunity. Their formation, according to immunologists, occurs according to three main mechanisms:
- Genetic conditioning without antigenic stimulus.
- The reaction of the body to minor attacks of infections that are unable to cause the disease.
- The response of the human body to the group effect of microorganisms or food antigen.
Chemical structure of antibodies
Antibodies are closely related to the fraction of Y-globulinwhey protein. In his absence, a disease arises agammaglobulinemia, in which antibodies are not produced by the body. Immunoglobulins are divided into five, different in chemical structure and biological functions, classes: G, A, M, D, E.
Immunoglobulins of class G, or igG antibodies, play the most important role in the formation of immunity in the manifestation of various forms and types of diseases.
Accumulation of antibodies igG in the body occursgradually. At the very beginning of the disease, their number is small. But as the clinical picture develops, the number of antibodies begins to grow rapidly, providing a protective function of the body.
Structure of immunoglobulins
The structure of an immunoglobulin of class G isa monomer molecule of 4 polypeptide protein bonds. These are two pairs, each consisting of one heavy and one light chain. At the end of the chains, each pair has a section, the so-called "active center". The center is responsible for communication with the antigen that causes the formation of antibodies. Antigens igG have two "active centers" at their endings. Consequently, they are divalent and are capable of binding two antigen molecules. Antibodies are a neutralizing factor of infectious manifestations.
Under the electron microscope, the molecule igG hasThe shape of an elongated ellipse with blunt ends. The configuration in the space of the active part of the antibody resembles a small cavity corresponding to the antigenic determinant, as the keyhole corresponds to the key.