Syngeneic transplantation of rat pancreatic islets into the spleen. Light and electron microscopical findings.

An islet transplantation model was established with the two congeneic Lewis rat strains LEW.1W and LEW.1A, which were made diabetic by a single i.p. injection of 50 mg/kg b.w. streptozotocin. Isolated neonatal islets of the two strains served as a graft. Syngeneic transplantation into the spleen resulted in permanent graft survival and in normoglycemia of streptozotocin diabetic rats of the two strains. 200 days after transplantation functionally intact islets were demonstrable in the spleen by histological, histochemical and electron microscopical investigations. Histochemical findings indicate an activation of interdigitating reticular cells in the white pulp and of macrophages in the red pulp of the spleen as consequences of the islet transplantation. In addition a few electron microscopical findings concerning possible interactions between host plasma cells, lymphocytes and transplanted beta cells of islets are described and discussed.