EFFECT OF INTERFERON-GAMMA AND GLUCOSE ON MAJOR HISTOCOMPATIBILITY COMPLEX CLASS-I AND CLASS-II EXPRESSION BY PANCREATIC BETA-CELLS AND NON-BETA-CELLS

Surface major histocompatibility complex (MHC) class I and class II ex pression by pancreatic islet cells is considered a local initiator or regulator of immune processes that can lead to diabetes. Locally relea sed cytokines, in particular interferon-gamma, are known to stimulate MHC antigen expression by islet cells. The present study quantifies MH C expression in cultured pancreatic beta- and non-beta-cells from both rat and human organs. Interferon-gamma increased MHC class I expressi on in endocrine beta- and non-beta-cells as well as in pancreatic duct al cells. The cytokine induced a 6-fold increase in the MHC class I me ssenger ribonucleic acid levels in pancreatic beta-cells; this effect was 2-fold amplified in the presence of elevated glucose levels (20 mm ol/L instead of 6 mmol/L). No MHC class II expression was observed in endocrine beta- or non-beta-cells; human, but not rat, ductal cells ex hibited MHC class II expression that increased in the presence of inte rferon-gamma. These data indicate that the increase in beta-cell MHC c lass I expression described in the pancreata of diabetic patients may result from stimulated transcription after exposure to locally release d interferon-gamma and/or to a hyperglycemic state. The association of human islets with ductal cells in which MHC class II expression is st imulated by interferon-gamma makes these cells potential participants in the autoimmune process in diabetes.