Activation of Insulin-Reactive CD8 T-Cells for Development of Autoimmune Diabetes

OBJECTIVE-We have previously reported a highly diabetogenic CD8 T-cell clone, G9C8, in the nonobese diabetic (NOD) mouse, specific to low-avidity insulin peptide B15-23, and cells responsive to this antigen are among the earliest islet infiltrates. We aimed to study the selection, activation, and development of the diabetogenic capacity of these insulin-reactive T-cells. RESEARCH DESIGN AND METHODS-We generated a T-cell receptor (TCR) transgenic mouse expressing the cloned TCR V alpha 18/V beta 6 receptor of the G9C8 insulin-reactive CD8 T-cell clone. The mice were crossed to TCRC alpha(-/-) mice so that the majority of the T-cells expressed the clonotypic TCR, and the phenotype and function of the cells was investigated. RESULTS-There was good selection of CD8 T-cells with a predominance of CD8 single-positive thymocytes, in spite of thymic insulin expression. Peripheral lymph node T-cells had a naive phenotype (CD44(lo), CD62L(hi)) and proliferated to insulin B15-23 peptide and to insulin. These cells produced interferon-gamma and tumor necrosis factor-alpha in response to insulin peptide and were cytotoxic to insulin peptide-coated targets. In vivo, the TCR transgenic mice developed insulitis but not spontaneous diabetes. However, the mice developed diabetes on immunization, and the activated transgenic T-cells were able to transfer diabetes to immunodeficient NOD.scid mice. CONCLUSIONS-Autoimmune CD8 T-cells responding to a low-affinity insulin B-chain peptide escape from thymic negative selection and require activation in vivo to cause diabetes. Diabetes 58:1156-1164, 2009