Expression of class II major histocompatibility complex antigens on pancreatic B cells in the NOD mouse

To elucidate the role of class II major histocompatibility complex antigen expression on pancreatic B cells in the development of diabetes in the non-obese diabetic (NOD) mouse, indirect immunofluorescence was employed for I-A staining on Bouin-fixed pancreas sections of NOD mice (I-A of which was reported as d), B10.GD (I-A, d), BALB/c (I-A, d) and C3H/He (I-A, k). I-A positive islets were observed in all NOD mice examined. Positive reaction was detected in islets both with and without lymphocytic infiltrations. Double staining with anti-insulin, glucagon, somatostatin or pancreatic polypeptide antibodies revealed that I-A positive cells corresponded with insulin cells, while other types of pancreatic islet cells were virtually negative for I-A. Weaker staining was seen in islets of B10.GD and, to a lesser extent, in those of BALB/c mice. C3H/He mouse islet cells showed no I-A expression. These results demonstrated the expression of I-A antigens on pancreatic B cells in the NOD mouse.