The effect of steroids on the regulation of major histocompatibility complex-class II expression on nonlymphoid...

The induction of MHC-class II antigens on human nonlymphoid tissues plays an essential role during the inhibition and augmentation of the immune response. Steroids have long been shown to possess strong immunosuppressive properties and successful steroid treatment has been associated with the absence of MHC-class II antigens on grated tissues. In this study we more specifically investigated the effect of steroids on the regulation of MHC-class II expression on nonlymphoid tissue. First, the influence of prednisolone on the induction process of the MHC-class II antigens on nonlymphoid tissue was determined. For this purpose vascular endothelial cells, kidney epithelial cells, fibroblasts, and a human colon tumor cell line were incubated with rIFN-gamma or primary MLC supernatant in the absence or presence of different concentrations of prednisolone. It was demonstrated that the induction process of MHC-class II antigens on these cell types was not affected by the drug at the different concentrations tested (1, 10, and 100 micrograms/ml). Next, the effect of prednisolone on the production of MHC-class II inducing factors was investigated. The drug was added at initiation of culture to primary MLC and the MHC-class II-inducing capacity of the supernatants was determined on day 7. Prednisolone at concentrations of 0.5-100 micrograms/ml clearly inhibited the overall production of factors responsible for MHC-class II induction on nonimmunological cells. The drug inhibited the production of IFN-gamma as well as non-IFN-gamma MHC-class II-inducing mediators. At a concentration of 1 microgram/ml the production of IFN-gamma and non-IFN-gamma MHC-class II-inducing mediators was reduced by, respectively, 85 per cent and 75 per cent. At a concentration of 10 micrograms/ml the production of both IFN-gamma and non-IFN-gamma mediators was almost completely inhibited. It is concluded that steroids downregulate the expression of MHC-class II antigens on nonlymphoid tissue by the inhibition of the production of MHC-class II-inducing mediators. However, once these mediators are present, the induction process itself is not affected by the drug.