Immunoglobulins (antibodies) are special proteins that are secreted by cells of the immune system to protect against foreign agents (microorganisms, toxins).

Depending on the function performed, there are 5 types of antibodies: A, D, E, G, M. IgA is formed in the mucous membranes (oral cavity, urogenital system, intestines...) in response to local exposure to potential "pests". Antibodies bind to these foreign invaders and prevent them from attaching to the surface of cells, thus preventing their entry into the internal environment of the body. Thus, IgA is responsible for local immunity - in the oral cavity, in the urogenital system, in the gastrointestinal tract. Once in the blood, IgA neutralizes bacteria and viruses, triggering a cascade of immune reactions (alternative pathway of complement).

The blood contains only 50% of the total amount of immunoglobulin A in the body. Class A antibodies do not pass through the placenta into the fetus, so the baby receives the necessary immunoglobulins with the mother's milk, which provides the baby with local protection Low levels of IgA indicate decreased local immunity of a temporary or permanent nature, increased breakdown of immunoglobulin, and that it is in a bound state with immune complexes. Selective IgA deficiency is one of the most frequent forms of immunodeficiency.

There is evidence that 1:400 to 1:500 Caucasoid race representatives suffer from this pathology in one form or another. As a rule, IgA deficiency is manifested by frequent infectious diseases of the respiratory system (bronchitis, pharyngitis, sore throat, pneumonia) and gastrointestinal tract in the form of diarrhea.