In certain circumstances, the immune mechanisms play an important role in protecting the body from various harmful effects, which can cause adverse reactions. So, the rejection of transplanted tissues and organs associated with immune incompatibility. When tissue incompatibility organism produces antigens to the alien tissue antibodies, which, together with the lymphoid cells cause damage and death. Current data for some diseases (systemic lupus erythematosus, thrombocytopenic purpura, periarteritis nodosa, autoimmune glomerulonephritis, ulcerative colitis, rheumatoid arthritis, etc.) may be considered as autoimmune processes arising out of the release contained in the body of specific antigens. In normal conditions, these antigens are bound and immunopathological reactions do not cause. In connection with these reasons came the development of a new search direction drugs that inhibit immunegenesis suppressing the production of antibodies because antibodies produced by lymphocytes and plasma cells, immunosuppressive activity must have chemical compounds that suppress the proliferative processes in the lymphoid (immune) tissue and suppress the biosynthesis of nucleic acids. As it turned out, immunodepressivne affected by many substances.

Klassificeret them as follows: suppress the immune response in General (e.g. cytostatics), which have a specific immunosuppressive effect (including antilimfocitarnyi serum), eliminating reactions accompanying the immune processes, has anti-inflammatory and partially immunosuppressive effect (e.g. glucocorticoids).

Especially pronounced immunosuppressive activity inherent to the cytostatics (see ANTINEOPLASTIC agents) — alkylating agents (cyclophosphamide, chlorambucil, thiotepa, propecia chloride, etc.), antimetabolites (mercaptopurine, fluorouracil, etc.), certain antibiotics (dactinomycin, etc.). Representatives of these groups are currently used as immunosuppressants. Specific immunosuppressant is azathioprine, similar in structure and action to 6-mercaptopurine. Immunosuppressive drugs can reduce the incompatibility of fabrics and to be very effective in the treatment of autoimmune diseases. However, current products do not have the selective action, and their application may be accompanied by side effects. They suppress the production of interferon, inhibit the formation of blood (leading to leukopenia, thrombocytopenia, anemia, and even pancytopenia), possibly lowering the overall immune function, activation of secondary infection, the development of septicemia, with long-term use they can contribute to the development of malignant tumors. Immunosuppressants (cytostatics, including azathioprine, etc.) must apply strict conditions with observance of necessary precautions.