IFN-gamma induces islet cell MHC antigens and enhances autoimmune, streptozotocin-induced diabetes in the mouse

To explore the role of the lymphokine, IFN-gamma, in the development of autoimmune-mediated insulin-dependent diabetes, we examined the effects of systemically administered IFN-gamma on the clinical features and pancreatic immunohistology of CBA mice made diabetic with multiple low doses of the pancreatic islet beta-cell toxin, streptozotocin. Mice given streptozotocin and IFN-gamma were significantly more hyperglycemic than those given streptozotocin alone and had significantly decreased body weight. Mice given IFN-gamma alone did not differ in glycemia or weight from vehicle-injected mice. On day 11, Ia proteins were detected on islet cells from mice given streptozotocin and their expression was potentiated by IFN-gamma; they could not be detected on islet cells from mice given IFN-gamma alone or vehicle. H-2K protein expression was increased on islet cells from mice given streptozotocin and was potentiated by IFN-gamma. IFN-gamma alone also increased H-2K protein expression on islet cells compared with vehicle-treated mice. These findings show that IFN-gamma enhances the severity of diabetes in mice given multiple-low doses of streptozotocin, in association with enhanced expression of Ia and H-2K proteins on islet cells. They indicate an important role for IFN-gamma in amplifying the autoimmune process leading to beta-cell destruction in diabetes. The ability of IFN-gamma to worsen autoimmune disease has implications for its use in man.