The target cell response to cytokines governs the autoreactive T cell repertoire in the pancreas of NOD mice

The pancreatic beta cell response to cytokines is crucial for the development of type 1 diabetes in the NOD mouse. For example, beta cell production of suppressor of cytokine signalling-1 (SOCS-1) protects against diabetes. This finding and other recent studies indicated that cytokine-stressed beta cells might contribute to disease progression by affecting the pancreatic lymphocyte infiltrate. The aim of this study was to provide insight into how the beta cell influences the pancreas-infiltrating T cell repertoire. Lymphocytes isolated from Socs1-transgenic (tg) and non-tg NOD mice were analysed by flow cytometry. mRNA and protein levels in pancreatic islets were measured by real-time PCR and immunofluorescence analysis, respectively. The percentages of regulatory T cells, total counts and ratios between infiltrating CD8+ and CD4+ T cells, and the expression of killer cell lectin-like receptor subfamily K, member 1 (NKG2D) on CD8+ T cells did not differ in pancreases from prediabetic Socs1-tg and non-tg NOD mice. However, a striking difference in the percentages of CD8+ T cells specific for glucose 6-phosphatase catalytic subunit-related protein 206-214 was found, showing that SOCS-1 prevents the accumulation of high percentages of self-reactive CD8+ T cells in the pancreas. It was also found that protection from diabetes in Socs1-tg NOD mice correlated with a reduced expression of Cxcl10 mRNA in IFN-gamma treated islets. This study highlights an important role for the beta cell in the local regulation of the diabetogenic process. By responding to the pro-inflammatory pancreas milieu it strongly influences the islet-reactive T cell repertoire in the pancreas.