MHC class II antigen expression on the various cells of normal and activated isolated pancreatic islets.

It is the aim of this study to characterize and quantify the cells within isolated rat islets that express MHC class II antigens. A set of five monoclonal antibodies and two polyclonal antisera of defined specificity were used in combination with a newly devised procedure for three-dimensional immunofluorescence evaluation of intact islets. It is shown that in addition to passenger cells, such as lymphocytes, macrophages, and dendriticlike cells, vascular endothelial and endocrine cells are also capable of expressing class II antigens. This expression is strongly influenced by in vitro culture, pregnancy, streptozotocin-induced diabetes, transplantation trauma, and alloantigenic stimuli. The possible role of the above cells in antigen presentation related to islet transplantation is discussed.