Anti-insulin receptor antibodies in human diabetes

Sera and immunoglobulin G from 10/104 diabetic patients (five with insulin-dependent, five with non-insulin-dependent diabetes) were found to contain antibodies that bound 125I-labelled purified human placental insulin receptors. Nine of these sera failed to inhibit insulin binding to cultured rat hepatocytes and did not stimulate glucose oxidation in rat adipocytes. Only one serum modestly inhibited insulin binding and stimulated glucose oxidation. These results suggest that sera from nine of these 104 diabetics contained a new type of anti-insulin receptor antibodies (AIRA) which bound to a locus different from the insulin binding site, and that only one of the 104 diabetic sera contained a low titer of conventional AIRA which could cause a clinical condition not distinguishable from ordinary non-insulin-dependent diabetes.