Detection of islet cell autoantibodies in newly diagnosed diabetic patients using insulin-producing Syrian hamster cells

Abstract

An insulin-producing cell line, Clone-16, of hamster origin, was characterized for islet hormone production and for reactivity with islet cell surface (ICSA) and islet cell cytoplasmic (ICA) antibodies in sera from children with newly diagnosed insulin-dependent (Type 1) diabetes mellitus (IDDM). The Clone-16 cells have a doubling time of about 50-60 hr. The cells produced 63 +/- 3 ng (mean +/- SD) immunoreactive insulin and 9.4 +/- 0.3 ng immunoreactive glucagon per day per 10(6) cells, while somatostatin (SRIF) and pancreatic polypeptide (PP) were undetectable. The reactivity with autoantibodies in IDDM sera was assessed by indirect immunofluorescence or 125I-protein A binding assay on intact cells to detect islet cell surface antibodies (ICSA) or on frozen sections of cell pellets to detect islet cell cytoplasmic antibodies (ICCA) by indirect immunofluorescence. Although the proportion of the ICSA-positive Clone-16 cells compared favorably with rat islet cells (r = 0.81; p less than 0.01), we found 5/10 IDDM sera to be positive on rat islet cells but 8/10 on the Clone-16 cells. There was also a good correlation in the 125I-protein A binding assay between mouse islet cells and Clone-16 cells (r = 0.91; p less than 0.01). Frozen sections of Clone-16 cells showed a cytoplasmic immunofluorescence in 8/10 of the IDDM sera and this reaction parallelled the results obtained in the standard indirect immunofluorescence assay with a frozen section of human blood group O pancreas. We conclude that the insulin- and glucagon-producing Clone-16 cells are a useful cell line for detecting islet cell autoantibodies.