Specific globulins formed by the body under the action of an antigen are called antibodies. Their special properties include the ability to combine with the antigen that caused their formation, as well as ensuring the protection of the body from the effects of infectious pathogens. Antibodies are neutralizers of infectious agents, reducing 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-accepting, or incomplete. This is a category of blocking antibodies. They do not give a visible reaction at the moment of connection with the antigen.
The content of antibodies in human blood serum
Antibodies have different effects on microorganisms: antitoxic, antimicrobial and anticellular. There are antibodies that neutralize viruses and immobilize spirochetes.
Differentiate antibodies into those thatglue red blood cells (hemagglutinins), dissolve red blood cells (hemolysins), and kill animal cells (cytotoxins).
Autoantibodies act against one's own protein in the destruction of organs and tissues. They are produced by releasing an antigen when the body's chemical structure changes.
Circulating antibodies can be detected in blood serum. This is an antibody test based on immunological reactions such as complement fixation, precipitation or agglutination. It shows both intracellular and surface-bound forms.
Immunity. Antibody functions
The blood serum of a practically he althy 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 body's response to minor attacks of infections unable to cause disease.
- The response of the human body to a group effect of microorganisms or a food antigen.
Chemical structure of antibodies
Antibodies are closely related to the Y-globulin fraction of whey protein. In its absence, the disease agammaglobulinemia occurs, in which antibodies are not produced by the body. Immunoglobulins are divided into five classes, different in chemical structure and biological functions: G, A, M, D, E.
G class immunoglobulins, or igG antibodies, play the most important role in the formationimmunity in the manifestation of various forms and types of diseases.
The accumulation of igG antibodies in the body occurs gradually. 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 class G immunoglobulin is a monomer molecule of 4 polypeptide protein bonds. These are two pairs, each of which consists of one heavy and one light chain. At the ends 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. igG antibodies have two "active centers" at their ends. Therefore, they are bivalent and are capable of binding two antigen molecules. Antibodies are a neutralizing factor in infectious manifestations.
Under the electron microscope, the igG molecule has the shape of an elongated ellipse with blunt ends. The configuration in space of the active part of the antibody resembles a small cavity corresponding to the antigenic determinant, like a keyhole corresponds to a key.
