Major histocompatibility complex protein expression on pancreas and pancreatic islet endocrine cell subsets

To determine which cells in the human and rat pancreas and islets express class I and II histocompatibility complex proteins, double indirect immunofluorescence and the Staphylococcus aureus rosette method were used. Islet preparations used permitted positive endocrine and class I or II protein identification. Class I and II proteins were expressed in pancreatic vascular endothelium and passenger cells of the mononuclear cell type. Antibodies directed to class I or beta 2 microglobulin reacted with dispersed islet B, A, and D cells, whereas class II protein antibodies were associated with only islet B and A cells. Islet B-cell class II proteins decreased after 20 days of in vitro culture. These results suggest that 1) a variety of pancreas and islet nonendocrine cells can express class I and II proteins, 2) normal pancreatic islet endocrine cells not only express class I proteins but also class II proteins, and 3) in vitro islet culture results in reduced expression of class II proteins by islet B cells.