A multiplicity of protein antigens in subcellular fractions of rat insulinoma tissue are able to stimulate T cells obtained from non-obese diabetic mice

Abstract

Type 1 (insulin-dependent) diabetes mellitus is a T-cell mediated autoimmune disease with a number of different proteins being implicated as target autoantigens. A 38 kDa protein residing in the insulin secretory granule of insulinoma tissue is recognized by T-cell clones from a newly-diagnosed Type 1 diabetic patient. We have investigated the capacity of normal rat pancreatic beta-cell extracts and various subcellular fractions of transplantable RIN tissue to induce proliferation of T cells from non-obese diabetic (NOD) mice and H-2 identical NON.NOD-H-2g7 control mice. Normal rat islet beta-cell protein fractions induced intense, dose-dependent proliferation of NOD splenic T cells, but only marginal proliferative responses of NON.NOD-H-2g7 splenic T cells. To further localize the target antigens, four different subcellular fractions from RIN tissue were used as a source of antigen; here in particular the cytosolic proteins showed dose-dependent activation capacity with splenic T cells in NOD animals. These activities were absent in control mice. There was no proliferation after incubation with microsome preparations from other rat endocrine tissues. Purified carboxypeptidase H did not have any stimulatory activity on NOD T cells. Fractionation of the RIN cytosolic proteins showed a large number of different fractions eliciting proliferative activity. These results demonstrate that NOD T cells respond to a large number of potential islet beta-cell target antigens and it will be necessary to utilize NOD T-cell clones to identify the number and nature of these antigens.