Detection of islet cell surface antibodies by an indirect rosette assay, using islet cells and protein A-labeled sheep red blood cells

An indirect rosette assay for detecting islet cell surface antibodies (ICSA), the autoantibodies directed to the membranous antigens of islet cells, has been developed. In this assay, Protein A-conjugated sheep red blood cells (SRBC) were used. Both viable and fixed SRBC were available. The results obtained using this new method in insulin-dependent diabetes mellitus (IDDM) patients were not only sensitive, but also correlated with results of the indirect immunofluorescence method currently used for detecting ICSA. Furthermore, in studies of streptozotocin-treated diabetic mice or rats, the courses of ICSA appearance were succesively demonstrated by this indirect rosette formation assay. Special advantages of this method are that materials are easily obtained and cost-effective, as the sample volume is small and the number of islet cells required is also small. Assays can be readily performed without a need for radioisotopic or fluorescent equipment. This method provides a reliable laboratory test for diagnosis of autoimmune diabetes mellitus.