BILE REGULATES THE EXPRESSION OF MAJOR HISTOCOMPATIBILITY COMPLEX CLASS-II MOLECULES ON RAT INTESTINAL EPITHELIUM

Background & Aims: Major histocompatibility complex (MHC) class II mol ecules are expressed on intestinal epithelial cells, and the intensity of this expression is regulated. The aim of this study was to test th e hypothesis that bile regulates the expression of MHC class II molecu les on intestinal epithelium. Methods: Rats were deprived of intestina l bile by external drainage for 24 or 48 hours, and their intestines w ere collected, sectioned, and stained with the anti-MHC class II monoc lonal antibodies OX4 and OX6. For one group of rats, bile flow was dev iated from its usual entry point to the ileum. Results: Compared with intact animals, MHC class II expression was observed to be diminished within 24 hours and totally absent after 48 hours of bile drainage. Fo r the group in which bile flow was deviated to the ileum, staining was only observed in the region distal to the entry point. Analysis by bi oassay and enzyme-linked immunosorbent assay of bile showed the presen ce of tumor necrosis factor and interferon gamma, respectively. Conclu sions: It is concluded that the presence of bile is required for the e xpression of MHC class II molecules on gut epithelium and that the cyt okine components of bite may be the inducing agents.