Immunosuppression

Immunosuppression
Intervention
Micrograph showing an opportunistic infection due to immunosuppression - large (blue) cell below-center-left infected with a polyomavirus. Urine cytology specimen.
MeSH	D007165
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Immunosuppression is a reduction of the activation or efficacy of the immune system. Some portions of the immune system itself have immunosuppressive effects on other parts of the immune system, and immunosuppression may occur as an adverse reaction to treatment of other conditions.

In general, deliberately induced immunosuppression is performed to prevent the body from rejecting an organ transplant, treating graft-versus-host disease after a bone marrow transplant, or for the treatment of auto-immune diseases such as systemic lupus erythematosus, rheumatoid arthritis, Sjögren's syndrome, or Crohn's disease. This is typically done using medications, but may involve surgery (spleen removal), plasmapharesis, or radiation.

A person who is undergoing immunosuppression, or whose immune system is weak for other reasons (for example, chemotherapy or HIV), is said to be immunocompromised. An immunosuppressant is any agent that weakens the immune system, including immunosuppressive drugs and some environmental toxins.

Administration of immunosuppressive medications or immunosuppressants is the main method of deliberately induced immunosuppression. In optimal circumstances, immunosuppressive drugs are targeted only at any hyperactive component of the immune system, and in ideal circumstances would not cause any significant immunodeficiency. However, in essence, all immunosuppressive drugs have the potential to cause immunodeficiency. Immunodeficiency can cause increased susceptibility to opportunistic infections and decreased cancer immunosurveillance. The term immunotoxin is also sometimes used (incorrectly) to label undesirable immunosuppressants, such as various pollutants. Immunosuppressants may be prescribed when a normal immune response is undesirable, such as in autoimmune diseases.