CELL STRESS-REGULATED HUMAN MAJOR HISTOCOMPATIBILITY COMPLEX CLASS-I GENE EXPRESSED IN GASTROINTESTINAL EPITHELIUM

Conventional major histocompatibility complex (MHC) class I genes enco de molecules that present intracellular peptide antigens to T cells. T hey are ubiquitously expressed and regulated by interferon gamma. Two highly divergent human MHC class I genes, MICA and MICB, are regulated by promoter heat shock elements similar to those of HSP70 genes. MICA encodes a cell surface glycoprotein, which is not associated with bet a(2)-microglobulin, is conformationally stable independent of conventi onal class I peptide ligands, and almost exclusively expressed in gast rointestinal epithelium. Thus, this MHC class I molecule may function as an indicator of cell stress and may be recognized by a subset of gu t mucosal T cells in an unusual interaction.