MODULATION OF MHC CLASS-II EXPRESSION IN HUMAN-CELLS BY DEXAMETHASONE

The effect of dexamethasone on human MHC class II expression was exami ned on various cell types including lymphocytes, monocytes, and epithe lial cells. Dexamethasone decreased the surface expression of HLA-DR a nd -DP, but not IFLA-DQ, on lymphocytic cell lines that constitutively express these molecules. In addition, dexamethasome down-regulated th e mRNA levels of HLA-DRA, but not of HLA-DQB, in Jijoye cells, a human lymphoblastic cell line. Similarly, dexamethasone decreased HLA-DR ex pression on epithelial and monocytic cell lines that express HLA-DR up on IFN-gamma treatment, In total, these results suggest that dexametha sone inhibits both constitutive and IFN-gamma-inducible MHC class II e xpression in several cell types. Moreover, these results indicate that the inhibitory effect of dexamethasone on MHC class II expression is selective for HLA-DR and -DP but not HLA-DQ. Possible mechanisms of de xamethasone-mediated regulation of MHC class II expression are discuss ed. (C) 1995 Academic Press, Inc.