Immunosuppressive agents

Immunosuppressive agents

Immunosuppressive agents are those that suppress immune response. They are used in transplantation surgery and in situ-ations that require suppression of host immunity. The agents are as follows:

X-irradiation: Sublethal dose of irradiation is toxic to replicat-ing cells and is used to suppress antibody formation. Antibody production ceases after 24 hours of receiving irradiation.

Radiometric drugs: These include alkylating agents (such ascyclophosphamide, nitrogen mustard, etc.), which suppress antibody production. Cyclophosphamide, given for 3 days, completely suppresses the antibody response. It selectively prevents replication of B cells.

Corticosteroids: Corticosteroids are anti-inflammatory drugsthat diminish the responsiveness of both B and T cells. They alter maturation of activated cells by suppressing the production of interleukins. They suppress delayed hypersensitivity, but in therapeutic doses for a short period, they have little effect on the production of antibodies.

Antimetabolites: These include folic acid antagonists (such asmethotrexate); analogs of purine (6-mercaptopurine and azathi-oprine); and analogs of cytosine (cytosine arabinose); and uracil (5-fluorouracil). These substances inhibit DNA and RNA syn-thesis, thereby inhibiting the cell division and differentiation, which is essential for cellular and humoral immune responses. These are usually used for prevention of graft rejection.

Antilymphocyte serum: Antilymphocyte serum (ALS) is aheterogeneous antiserum raised against T lymphocytes. The ALS acts mainly against circulating lymphocytes but not against lymphocytes in lymphoid organs. It is mainly used to prevent graft rejection in transplantation surgery.