immunosuppressant

An immunosuppressant turns the immune system's activity down. Most of the time a strong immune system is a good thing, but sometimes it works against us: it can reject a transplanted organ as foreign, or it can mistakenly attack the body's own tissues in autoimmune disease. An immunosuppressant calms this response, accepting a weaker defence in exchange for stopping harmful immune activity.

These drugs span several mechanisms. Glucocorticoids broadly dampen inflammation and immune-cell activity. Calcineurin inhibitors such as ciclosporin and tacrolimus block a signal T cells need to switch on. Antiproliferative agents like azathioprine and mycophenolate starve dividing immune cells, and several monoclonal antibodies neutralise specific immune signals. They are used after organ transplantation and in conditions like lupus, rheumatoid arthritis and inflammatory bowel disease.

The central trade-off is obvious: a quieter immune system fights infections and cancers less well. Patients on long-term immunosuppressants face higher risks of serious infections and some malignancies, so dosing aims for the lowest effective level, often with drug-level monitoring for agents like tacrolimus that have a narrow therapeutic window.