Innate immunity is a specific feature of a person and is present in them from birth, and not as a result of a disease. In contrast, acquired immunity arises in the course of life, a person is not born with it. Cytokines are cells that regulate immune response by modulating the immune response modulated by them. The primary immune response is the production of antibodies and the subsequent binding of antigens to antibodies – as a reaction to the first encounter with a new antigen. A secondary immune response develops after repeated contact with the same antigen, as a result of which the number of antibodies immediately increases sharply, and high–specificity immunoglobulins – IgG are synthesized.
There are three ways to activate this system: classical, alternative and lectin. In the classical version, complement is activated through IgG and IgM, which form immune complexes with antigens. With an alternative pathway, complement activation occurs without the participation of antibodies. it is formed by the surface molecules of microbes and their extracellular structures — for example, hydrocarbons, polysaccharides, etc. The lectin pathway is activated through lectin binding mannose or a group of Ficolin lectins that bind molecules on the surface of pathogens — yeast, bacteria, parasites and viruses. To help defeat bacteria, C3b performs the function of opsonin, and C3a works as anaphylatoxin, which is able to affect mast cells with the release of histamine.