Kinetics of TNF-alpha and IFN-gamma mRNA expression in islets and spleen of NOD mice

Abstract

Insulin-dependent diabetes mellitus is caused by autoimmune destruction of pancreatic β cells. Non-obese diabetic (NOD) mice spontaneously develop diabetes similar to the human disease. Cytokines produced by islet-infiltrating mononuclear cells may be directly cytotoxic and can be involved in islet destruction coordinated by CD4+ and CD8+ cells. We utilized a semiquantitative RT-PCR assay to analyze in vitro the mRNA expression of TNF-α and IFN-γ cytokine genes in isolated islets (N = 100) and spleen cells (5 × 105 cells) from female NOD mice during the development of diabetes and from female CBA-j mice as a related control strain that does not develop diabetes. Cytokine mRNAs were measured at 2, 4, 8, 14 and 28 weeks of age from the onset of insulitis to the development of overt diabetes. An increase in IFN-γ expression in islets was observed for females aged 28 weeks (149 ± 29 arbitrary units (AU), P<0.05, Student t-test) with advanced destructive insulitis when compared with CBA-j mice, while TNF-α. was expressed in both NOD and CBA-j female islets at the same level at all ages studied. In contrast, TNF-α in spleen was expressed at higher levels in NOD females at 14 weeks (99 ± 8 AU, P<0.05) and 28 weeks (144 ± 17 AU, P<0.05) of age when compared to CBA-j mice. The data suggest that IFN-γ and TNF-α expression in pancreatic islets of female NOD mice is associated with β cell destruction and overt diabetes.