In addition to the effects on T lymphocytes, Cyclosporin A can inhibit dendritic cells allostimulatory capacity, but its precise mechanism remains unknown. The data in this study demonstrated that Cyclosporin A has no effect on the expression of major histocompatibility complex class II and costimulatory molecular CD80, CD86, CD40 on matured DC induced by Lipopolysaccharide in vitro, but can up-regulated B7-DC expression on DC in an Interleukin-4-dependent manner, which is associated with reduced allostimulatory ability of DC. Furthermore, Cyclosporin A treatment inhibited production of Interferon-gammaand TNF-alpha, Interleukin-12p70, but increased production of the Interleukin-10 of DC. Thus, up-regulated expression of B7-DC may be responsible for Cyclosporin A-mediated inhibitory effects on allostimulatory capacity of DC.