CHARACTERIZATION OF PANCREATIC LYMPHOCYTES-T ASSOCIATED WITH BETA-CELL DESTRUCTION IN THE NONOBESE DIABETIC (NOD) MOUSE

Pancreatic beta cell destruction in the non-obese diabetic (NOD) mouse is mediated by T lymphocytes and macrophages and accelerated by cyclophosphamide. We purified pancreatic T lymphocytes from the NOD mouse for comparative phenotypic and functional analysis with T lymphocytes from spleen, peripheral blood and regional lymph nodes. Pancreatic T lymphocytes from NOD-Wehi mice, which have an incidence of spontaneous diabetes of <5%, had a CD4:CD8 ratio of 1.25 ± 0.23 compared with 2.44 ± 0.31 for peripheral blood lymphocytes. After cyclophosphamide, the CD4:CD8 ratio of pancreatic lymphocytes increased to 2.30 ± 0.24 at day 7. T lymphocytes bearing IL-2 receptors increased two- to three-fold in number and their secretion of GM-CSF/IL-3 and IFN-γ increased to a maximum on day 7. Pancreatic insulin content and mRNA levels declined sharply between days 10 and 12, at which time the majority of pancreatic T lymphocytes in hyperglycaemic mice were CD8+ (CD4:CD8 ratio 0.63 ± 0.04 compared to 4.14 ± 1.05 in peripheral blood). The pancreatic T lymphocyte CD4:CD8 ratio in prediabetic NOD-Lt mice, which have an incidence of spontaneous diabetes of about 60% at 150 days, was similar to that in untreated NOD-Wehi mice, but 25% of their pancreatic CD8 T lymphocytes were IL-2-receptor positive. Thus, significant changes in the phenotype of NOD pancreatic T lymphocytes following cyclophosphamide were not reflected in peripheral blood or spleen T lymphocytes. The earliest change after cyclophosphamide was an increase in activated, predominantly CD4+ T lymphocytes; with the development of beta cell destruction and hyperglycaemia, pancreatic T lymphocytes were, as in human IDDM, predominantly CD8+. © 1991.