An Immunosuppressant is any substance that performs immunosuppression of the immune system. They may either be exogenous, as immunosuppressive drugs, or endogenous, as e. g. testosterone. When the immune system function is suppressed, there is an increased susceptibility to infectious diseases and cancers.
The term immunotoxin is also sometimes used (incorrectly) to label undesirable Immunosuppressants , such as various pollutants. Polychlorinated-biphenyls (PCB) and the herbicide DDT are Immunosuppressants.
Immunosuppressants may be prescribed when a normal immune response is undesirable, such as in autoimmune diseases.
After an organ transplantation, the body will nearly always reject the new organ(s) due to differences in human leukocyte antigen haplotypes between the donor and recipient. As a result, the immune system detects the new tissue as "hostile", and attempts to remove it by attacking it with recipient leukocytes, resulting in the death of the tissue. Immunosuppressants are applied as a countermeasure; the side effect is that the body becomes more vulnerable to infections and malignancy, much like in an advanced HIV infection.
Immunosuppressants are drugs that inhibit or prevent activity of the immune system. They are also used in immunosuppressive therapy.
Examples of Immunosuppressants are as follows: