Cytotoxic T-Cells from T-Cell receptor transgenic NOD8.3 mice destroy f-Cells via the perforin and fas pathways

Cytotoxic T-cells are the major mediators of f-cell destruction in type 1 diabetes, but the molecular mechanisms are not definitively established. We have examined the contribution of perforin and Fas ligand to f-cell destruction using islet-specific CD8+ T-cells from T-cell receptor transgenic NOD8.3 mice. NOD8.3 T-cells killed Fas-deficient islets in vitro and in vivo. Perforin-deficient NOD8.3 T-cells were able to destroy wild-type but not Fas-deficient islets in vitro. These results imply that NOD8.3 T-cells use both pathways and that Fas is required for f-cell killing only when perforin is missing. Consistent with this theory, transgenic NOD8.3 mice with f-cells that do not respond to Fas ligation were not protected from diabetes. We next investigated the mechanism of protection provided by overexpression of suppressor of cytokine signaling-1 (SOCS-1) in f-cells of NOD8.3 mice. SOCS-1 islets remained intact when grafted into NOD8.3 mice and were less efficiently killed in vitro. However, addition of exogenous peptide rendered SOCS-1 islets susceptible to 8.3 T-cell-mediated lysis. Therefore, NOD8.3 T-cells use both perforin and Fas pathways to kill f-cells and the surprising blockade of NOD8.3 T-cell-mediated f-cell death by SOCS-1 overexpression may be due in part to reduced target cell recognition