Dexamethasone inhibits IFN gamma-induced MHC class II expression of intestinal epithelial cells independently of the TGF-beta 1 regulatory pathway

Background: In the presence of inflammation, an increased expression of ent erocyte MHC class II is observed, leading to altered mucosal antigen handli ng, Corticosteroids are potent anti-inflammatory drugs, widely used in trea ting inflammatory bowel disorders, However, their diverse mechanisms of act ion are only partially understood, Aim: To evaluate effect and mechanisms of corticosteroids on intestinal cry pt epithelial cell MHC class II. Methods: The effect of dexamethasone treatment on cytokine-induced MHC clas s II expression was measured in IEC-6 cells by immunofluorescence and flow cytometry. To determine the role of the TGF-beta 1 pathway in mediating the effects of cytometry. regulatory dexamethasone, neutralizing anti-TGF-beta antibodies were used. Additionally, endogenous and dexamethasone-stimulate d IEC-6 cell TGF-beta 1 production was measured by ELISA. Results: Dexamethasone potently down-regulated IFN gamma-induced class II e xpression on IEC-6 cells, in a dose-dependent manner, TGF-beta 1 had a simi lar inhibitory effect on class II expression, However, neutralizing anti-TG F-beta antibodies did not alter the effect of dexamethasone, Furthermore, d examethasone reduced endogenous TGF-beta 1 synthesis. Conclusions: Corticosteroids inhibit cytokine-induced MHC class II expressi on on IEC-6 cells in a TGF-beta 1 independent way. This effect may markedly alter enterocytic antigen presentation, reducing the aberrant state of act ivation of mucosal immune cells.