Inhibitory effect of cyclosporin A on the OKT3-induced peripheral blood lymphocyte proliferation

In this paper we studied the effect of cyclosporin A (CyA) on interleukin 1 (IL-1) and interleukin 2 (IL-2) production and on IL-2 receptor expression by human peripheral blood lymphocytes induced to proliferate following OKT3 monoclonal antibody stimulation. CyA inhibited T-cell proliferation in a dose-dependent manner and its effect was inversely correlated with the entity of the mitogenic signal. The drug reduced not only IL-2 synthesis but also IL-1 production. CyA was also found to be able to inhibit the expression of IL-2 receptors on T cells. By supplementing with IL-1 and/or IL-2 the cultures carried out in the presence of CyA, it became evident that the inhibition of IL-2 production mainly depended on the CyA-induced reduction of IL-1 synthesis. Thus the IL-2 production by "resting" T cells had to be considered as an IL-1-dependent event. In addition it was found that the presence of IL-1 constituted a crucial requirement for the induction and the positive modulation of IL-2 receptor expression. Although IL-2 could play a role in facilitating the expression of IL-2 receptors, its effectiveness to do so depended on the presence of IL-1. In conclusion, CyA is to be considered not only as a potent immunodepressive drug but also as a valuable tool for the study of T-cell activation and proliferation.