Human insulin dependent diabetes mallitus (IDDM) is believed to represent the end stage of an autoimmune attack on the islets of Langerhans. Work in animal models of the disease has provided information related to the pathogenesis of the disease, and has indicated that the development of insulitis and hyperglycemia are T cell mediated. We plan to study this T cell dependent process in the murine multi-dose streptozotocin model (MDSDM), where we have previously shown that elimination of T cells prevents the disease. The objective of these studies is to identify the cells and antigens involved in the disease so that effective approaches to the treatment and prevention of diabetes can be developed. We will test the hypothesis that development of diabetes in MDSDM represents the recognition of islet antigens by a select group of T cells and that elimination of these cells will prevent the disease. The MDSDM model is uniquely suited for this analysis because the earliest events in the pathogenesis of the disease can be studied. In order to identify the cells that initiate diabetes, we will analyze the infiltration of T cells into islets during the induction of MDSDM. This will be done using oligonucleotides specific for Vbeta genes and the polymerase chain reaction, and with monoclonal antibodies specific for Vbeta gene products using flow cytometry. The significance of our findings will be tested by determining the ability of in vivo treatment with mAbs that deplete groups of T cells to prevent MDSDM. We have isolated a line of T cells that is activated by antigens present on islets or an insulinoma line, betaTC3, treated with streptozotocin. We will derive clonal populations from this line for purposes of characterizing islet reactive T cells and determining the mechanism of islet destruction. The relevance of these clonal populations to diabetes will be tested by their ability to transfer disease. The antigens recognized by the T cell clones will be isolated from MHC molecules and identified by their ability to sensitize P-815 cells to lysis by the islet reactive T cells. The sequence of protein antigens isolated in this manner will be determined. We plan to use antigen recognized by the T cell line to confer """"""""tolerance"""""""" to the development of MDSDM. Since cells reactive with self antigens are deleted (or at least inactivated) in the thymus during T cell ontogeny, we will place islet antigen in the thymus of mice susceptible to MDSDM and then induce maturation of new T cells by depleting mature peripheral T cells with monoclonal antibody. We will test the ability of this experimental manipulation to induce non-responsiveness to MDSDM. Thus, we will develop an understanding of the involvement of T cells and islet specific antigens in MDSDM. We will use this understanding to prevent diabetes in this model by elimination of T cells either with mAbs specific for the islet reactive T cells or by inducing deletion of islet antigen reactive T cells during T cell ontogeny in the thymus. These results should suggest new immunologic approaches which may be developed for use for the prevention of human IDDM.
