In situ islet T cell receptor variable region gene usage in the nonobese diabetic mouse

Several features of the genetics and immunopathology of diabetes in the nonobese diabetic (NOD) mouse, which spontaneously develops type I diabetes, are shared with the human disease. Immunohistochemical studies support the concept that T lymphocytes are the major components of inflammatory cells in the pancreatic islets and these cells may play a critical role in the destruction of the beta cells leading to diabetes. Therefore, we examined whether particular TCR-beta variable region genes were utilized by in situ islet T cells at different stages (4 - 5, 7, 14 - 15 and 16 weeks of age) of the disease process. Dot-blot hybridization was performed using RNA prepared from isolated islets, thymus, spleen, peripheral blood leukocytes and axillary lymph nodes of 10 to 15 mice pooled for each data point. Ten different TCR V-beta probes were used for the analyses. Limited usage of islet V-beta genes was observed only at the early prediabetic stage (4 - 5 weeks old) of the disease. At later stages of the disease (7 - 16 weeks old), no preferential usage of TCR genes was observed in the islets compared to those of peripheral lymphoid organs. These data suggest that only certain types of T cells bearing particular TCR V-beta genes may be responsible for initiating and perpetuating infiltration of immune cells into the islets and these particular T cells are only identified at the very early stages of the autoimmune process.