title: Suppression of in vitro lymphocyte reactivity by cyclosporin A: existence of a population of drug-resistant cytotoxic lymphocytes.
abstract: Cyclosporin A (CS-A) is an unusual endecapeptide isolated from the fungi Cylindrocarpon lucidum Booth and Trichoderma polysporum. It is a potent immunosuppressive drug that prevents rejection of kidney and heart allografts whilst having a low myelotoxicity. Its mode of action is still unclear but its main target appears to be the T lymphocyte. The mixed lymphocyte reaction (MLR) and cell-mediated lymphocytoxicity (CML) used here are generally regarded as in vitro correlates of allograft rejection. Our data show that CS-A is a powerful inhibitor of MLR reactivity, regardless of whether the cells were obtained from normal or presensitized donors; that the CML of lymph node cells is likewise totally inhibited if the drug is added early during cell culture; and that, by contrast, the cytotoxic response of spleen cells from presensitized but not from normal mice is only partially inhibited, even with a tenfold increase in dose. It is therefore suggested that there exists a population of cytotoxic spleen cells that is relatively resistant to the action of this drug.
mesh_terms: D000818:Animals; D002478:Cells, Cultured; D003524:Cyclosporins; D003602:Cytotoxicity, Immunologic / Q000187:drug effects*; D004305:Dose-Response Relationship, Drug; D007108:Immune Tolerance / Q000187:drug effects*; D008213:Lymphocyte Activation / Q000187:drug effects*; D007959:Lymphocyte Culture Test, Mixed; D051379:Mice; D010456:Peptides, Cyclic / Q000494:pharmacology*; D013601:T-Lymphocytes / Q000187:drug effects*
chemical_list: D003524:Cyclosporins; D010456:Peptides, Cyclic