In vitro effects of cyclosporin A on lymphocyte subpopulations. 1. Suppressor cell sparing by cyclosporin A.

The fungal metabolite, cyclosporin A, is a potent immunosuppressive compound. Experiments were performed in vitro with both human and nonhuman primate peripheral blood lymphocytes to study the effect of this agent on suppressor cell activity. Cyclosporin A did not affect the generation or function of concanavalin A-induced suppressor lymphocytes as measured by their ability to suppress thymidine uptake of lymphocytes in secondary cultures. No evidence of suppressor cell induction was noted by incubation of lymphocytes with only cyclosporin A. We conclude that, although cyclosporin A does not generate or induce suppressor cell lymphocytes, it does spare them, while inhibiting other subpopulations. This effect may create an imbalance in the immune system which results in profound suppression.