Abstract
By an indirect immunofluorescence method with In-111 cells (hamster insulinoma cell line), circulating islet cell surface antibodies (ICSA) were detected in 7 (20%) out of 36 patients with non-insulin dependent diabetes mellitus (NIDDM), 9% of 68 chronic thyroiditis (CT) patients, or 16% of 19 NIDDM patients associated with CT, but not in 18 normal subjects. Sera from five out of nine ICSA-positive patients examined further also showed cell-surface immunofluorescence on TPC-1 cells (human thyroid papillary adenocarcinoma cell line), and prior absorption of the sera with In-111 cells abolished the immunofluorescence. The 64kDa protein from In-111 cells or human thyroid follicular cells was immunoprecipitated with ICSA-positive sera. In one case of NIDDM associated with CT, 64kDa protein was detected in both cells. The results indicate that some ICSA in NIDDM patients recognize the same or a very closely-related autoantigen(s) in both islet β-cells and thyroid follicular cells, suggesting an explanation, at least in part, for the autoimmune mechanism(s) in clinical association of NIDDM and CT.
