We have used an insulinoma cell line, RIN-B, which expresses most of the putative IDDM autoantigens (GAD 65 and 67, insulin, CPH, 38 kDa insulin granule protein). ICA positive sera from IDDM patients are positive with RIN-B cells and it has been shown that T cells from IDDM patients have specific reactivity to RIN-B extracts which can specifically induce the proliferation of a T cell clone specific for the 38kDa of islet granules. The objective of this project is the study of the capacity of an endocrine epithelial cell to process and present target autoantigens to T cells. We are using the RIN cell line as the basis to construct a panel of transfectants expressing different combinations of HLA molecules DR4 or DR3, human B7 as a co-stimulatory molecule and the invariant chain (Ii) and HLA-DM so the class II molecules expressed are internally transported and loaded with peptide in a way similar to a normal APC. This panel of transfectants is being used to study: 1) the processing capacity of the cells as asessed by the analysis of peptides bound to HLA-DR4 or DR3 in the different transfectants and 2) their capacity to present antigen by inducing a primary allogeneic response from PBL or to activate the response of alloreactive, antigen specific and autoreactive T cell clones.