cyclosporin, any of a group of biologically active metabolites of Tolypocladium inflatum Gams and certain other fungi. Nine have been identified and are designated cyclosporin A through I. The major forms are cyclosporin A and C, which are cyclic oligopeptides with immunosuppressive, antifungal, and antipyretic effects. As immunosuppressants, cyclosporines primarily affect T lymphocytes. They are widely used in organ transplantation to suppress rejection and are known to be a human carcinogen. Also spelled ciclosporin.
