immunosuppression

n. suppression of the immune system's natural responses (Medicine)

Immunosuppression involves an act that reduces the activation or efficacy of the immune system. Some portions of the immune system itself have immuno-suppressive effects on other parts of the immune system, and immunosuppression may occur as an adverse reaction to treatment of other conditions. Deliberately induced immunosuppression is generally done 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 rheumatoid arthritis or Crohn's disease. This is typically done using drugs, but may involve surgery (splenectomy), plasmapharesis, or radiation.
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Immunosuppression /im·mu·no·sup·pres·sion/ prevention or diminution of the immune response, such as by radiation, antimetabolites, or specific [more]Immunosuppression - Community and Resources

Noun
1. lowering the body's normal immune response to invasion by foreign substances; can be deliberate (as in lowering the immune response to prevent rejection of a transplanted organ) or incidental (as a side effect of radiotherapy or chemotherapy for cancer)
(hypernym) immunological disorder

n. immunosuppression, suppression of the immune system's natural responses (Medicine)