Inhibition of phagocytes by cyclosporin in vitro

Cyclosporin is an immunosuppressant that acts by selectivelyinhibiting the activation of T lymphocytes. Its effects on monocytesand neutrophils are not well explored. We investigated the invitro effects of cyclosporin on these cells, harvested fromvenous blood from nine healthy, non-smoking volunteers. In vitroincubation of monocytes with increasing concentrations of cyclosporin(5, 25 and 625 µg) depressed their phagocytosis by 22%,32% and 49%, respectively, compared to the control values. Theintracellular killing capacity of monocytes decreased by 26%, 31 % and 43% with these doses, and neutrophilphagocytosis was depressed in a similar manner (16%, 30% and40%). Patients receiving cyclosporin are susceptible to infections,and inhibition of these phagocytic cells by cyclosporin maybe partly responsible for this. Neutrophil chemotaxis is reducedin patients with impaired renal function. Treating these patientswith cyclosporin may in addition suppress the phagocytic functionof these cells.