A new method of detection of islet cell antibodies (ICA) using peroxidase-labeled protein A, and incidence of ICA in type 1 (insulin-dependent) diabetes.

We have developed a new method of detecting islet cell antibodies using peroxidase-labeled protein A, and have determined the incidence of ICA in Type 1 (insulin-dependent) diabetes in Japan. In our method, fresh frozen sections of human pancreas and serum samples were incubated and then treated with peroxidase-labeled protein A at room temperature. Conjugates of peroxidase and protein A were subjected to Sephadex G-200 column chromatography, and only the 80,000 dalton peak was employed. The treated sections were allowed to react with haematoxylin and eosin (HE) to confirm the localization of islet cells. With this method, human pancreatic tissues can be used regardless of age and blood type, and the stained sections can be stored for more than 5 years. Serum samples obtained from 52 patients with Type 1 diabetes, 54 with Type 2 (non-insulin-dependent) diabetes and 100 control subjects were examined. In patients with Type 1 diabetes, islet cell antibodies were detected in 14 of 14 (0.5 years after onset), 3 of 6 (0.5-1 years after onset), 7 of 16 (1-5 years after onset) and 2 of 16 (more than 5 years after onset). In contrast, only 4 of 54 patients with Type 2 diabetes and none of the controls were ICA positive. It is concluded that, with our newly developed method using peroxidase-labeled protein A, ICA is present in all Japanese Type 1 diabetic patients whose diabetic manifestations are less than 0.5 years duration from onset.