Low-avidity autoreactive CD8 T-cells (CTL) escape from thymic negative selection and peripheral tolerance mechanisms are essential for their regulation. We report the role of proinsulin (PI) expression on the development and activation of insulin-specific CTL, in the NOD mouse model of type 1 diabetes (T1D). We studied insulin B chain-specific CD8 T-cells from different T-cell receptor transgenic mice (G9Cα-/-) expressing normal PI1 and PI2 or altered proinsulin expression levels. In the absence of PI2 (Ins2-/-), CTL in pancreatic lymph nodes (PLN) were more activated and male G9Cα-/- mice developed T1D. Furthermore, when the insulin-specific CTL developed in transgenic mice lacking their specific PI epitope, the CTL demonstrated increased cytotoxicity and proliferation in vitro and in vivo in the PLN after adoptive transfer into NOD recipients. DC-stimulated proliferation of insulin-specific T-cells was reduced in the presence of lymph node stromal cells (LNSC) from NOD mice but not from mice lacking the PI epitope. Our study shows that LNSC regulate CTL activation and suggests that exposure to proinsulin in the periphery is very important in maintenance of tolerance of autoreactive T-cells. This is relevant for human T1D and has implications for the use of antigen-specific therapy in tolerance induction.
- Received December 2, 2015.
- Accepted July 25, 2016.
- © 2016 by the American Diabetes Association.