Autoreactive Human TCR Initiate Insulitis and Impaired Glucose Tolerance in HLA DR4 Transgenic Mice

A human TcR derived from an autoreactive T cell specific for GAD65, from a subject at high risk for autoimmune diabetes, was introduced into HLA-DR4 transgenic mice. The source of TCR was a CD4 + T H 1 + T cell clone which responded to an immunodominant epitope of the human islet protein GAD65, an epitope shared with both GAD65 and GAD67 in the mouse. The resulting HLA-DR4/GAD-TcR transgenic mice on a Rag2 o/o /I-Ab o/o /B6 background exhibited a CD4 + infiltrate into pancreatic islets that correlated with a loss of insulin in infiltrated islets. These mice also exhibited a subclinical impaired tolerance to exogenously fed glucose as assayed by an intraperitoneal glucose tolerance test. T cells containing the GAD65/67 (555–567) responsive TcR undergo strong negative selection as evidenced by a 10-fold lower thymocyte cellularity compared to non-TcR transgenic mice, and clonotype peripheral T cells represented approximately 1 percent of CD4 + T cells in Rag2 sufficient mice. Upon in vitro stimulation, GAD65/67 555–567 responsive T cells secrete IFN-γ, minimal IL2 and TNFα and no IL4, IL5, IL10, or IL17, consistent with a T H 1 profile. These data demonstrate that CD4 + T cells specific for a naturally processed epitope within GAD can specifically home to pancreatic islets and lead to impaired islet beta cell function in diabetes-associated HLA-DR4 transgenic mice on the relatively non-autoimmune C57BL/6 background. The relatively slow progression and patchy insulitis are reminiscent of the chronic pre-clinical phase similar to a majority of human at-risk subjects, and models these indolent features of human T1D.