immunosuppression, reduction in the ability of the immune system to defend against disease or infection. Immunosuppression may be induced by certain diseases, such AIDS, lupus erythematosus, rheumatoid arthritis, or type 1 diabetes mellitus. Additionally, suppression of immunity often occurs as a result of treatment with certain types of drugs, including anticancer drugs and drugs used to prevent the rejection of an organ transplant.
In the case of therapy to prevent organ rejection, the aim is to allow the recipient’s body to accept the organ permanently with no unpleasant side effects. In some cases the dosage can be reduced or even stopped without causing rejection. Other uses of immunosuppressant drugs are in the treatment of certain autoimmune diseases and for the prevention of erythroblastosis fetalis. The main drawback of such treatments is the increased risk of infection for the duration of treatment and of lymphoma, in the case of long-term immunosuppression.