Interleukin-1 alpha inhibits the effects of gamma-interferon and tumor necrosis factor alpha on the expression of the major histocompatibility antigens by the rat endothelium.

Modulation of the major histocompatibility (MHC) antigen expression on rat endothelial cells by a mixture of cytokines has been examined. Experiments were performed employing both enzyme-linked immunoassay (ELISA) and fluorescence-activated cell-sorting (FACS) techniques and recombinant cytokines: interleukin-1 alpha (IL-1 alpha), tumor necrosis factor alpha (TNF alpha), and gamma-interferon (tau IFN). The results obtained show that TNF alpha enhances the effect of tau IFN on the expression of class I and II MHC antigens. IL-1 alpha did not affect tau IFN-induced class I expression but did inhibit tau IFN-induced class II expression. Finally, TNF alpha-induced class I MHC expression was inhibited strongly by IL-1 alpha. Pretreatment of endothelium with tau IFN did not potentiate the effects of IL-1 alpha or TNF alpha on the endothelial MHC antigen expression. These results suggest a possible anti-inflammatory role of IL-1 alpha via down-regulation of MHC antigen expression by the endothelium.