Although the introduction of cyclosporine A (CyA) and FK506 for immunosuppressive therapy has dramatically enhanced the early survival of organ transplant recipients, administration of these immunosuppresants is correlated with high incidence of transplant arteriosclerosis. Transplant-associated arteriosclerosis is believed to result from recipient inflammatory responses to the allograft, as it is characterized by early mononuclear cell infiltration of the transplanted vessel. We reported that vascular endothelial cells naturally express a death factor, Fas ligand, that may function to inhibit detrimental leukocyte infiltration. Here, we show that CyA or FK506 downregulates FasL expression on endothelial cells with accompanying decrease in the cytotoxicity toward Fas-bearing cells. Our findings not only demonstrate a novel biological action of these drugs, but also suggest a mechanism by which immunosupressive treatment contributes to atherogenesis.
Copyright 1999 Academic Press.