Cytoplasmic islet-cell antibodies, insulin antibodies, islet-cell surface antibodies and islet-cell specific cytotoxicity were determined in serum of the following groups: 131 patients with type I diabetes, 19 with type II diabetes, 29 with mumps, 29 with enterovirus infections, 18 with measles and 28 healthy controls. Cytoplasmic islet-cell antibodies were found predominantly in type I diabetics. Islet-cell surface antibodies, on the other hand, were relatively frequently (60-80%) present in sera of both diabetics and patients with various virus infections. Islet-cell specific cytotoxicity in vitro was found not only in sera of diabetics, but also of patients with mumps or enterovirus infections. Sera of five patients with measles, however, had cytotoxic reactions comparable to those of the controls. These results suggest that cytotoxic antibody reactions against islet cells in vitro occur also in sera of non-diabetic patients. Under certain circumstances, infections which induce such immune reactions may be of significance in the pathogenesis of diabetes.
