Critical Role of Superoxide (02-) Production in the Pathogenesis of Autoimmune Diabetes (T1D).

ALR mice are unusually resistant to T1D. Genetic elements responsible for the ALR-derived T1D resistance were identified via analysis of outcross/backcross cohorts of ALR with T1D-prone NOD. We have previously demonstrated that NADPH Oxidase (NOX) in ALR cells is inhibited. Genetic analyses have mapped inhibited NOX to a locus on Chromosome (Chr.) 3 [Suppressor of Superoxide Production (Susp)] that is also in linkage disequilibrium with ALR-derived T1D resistance. To directly determine the impact of NOX inhibition on T1D initiation, NOX-inactive NOD mice (NOD-Ncf1µ) were bred. NOD-Ncf1µ mice have significantly reduced incidence of T1D (10%) versus 85% in Ncf1 intact littermate controls and were resistant to the adoptive transfer of diabetogenic BDC2.5 CD4+ T cell clones, demonstrating that NOX plays an important role in T1D pathogenesis. To identify the gene encoded by Susp and determine the mechanism of protection, ten recombinant congenic strains (RCS), with overlapping intervals on Chr. 3, have been generated. ALR x NOD F1 hybrids demonstrated an intermediate O2• production compared to ALR (Low O2• production) and NOD (High O2• production) supporting co-dominant mode of inheritance. Using the RCS we have reduced the size of the interval containing Susp from 45 cM to 19 cM. Experiments have also been performed comparing immune system function from mice with and without NOX activity that result in T1D protection.. Splenocytes from NOD, NOD-Ncf1µ, and ALR mice were activated to assess cytokine production. Activation of NOD splenocytes led to a Th1 cytokine secretion profile as exemplified by higher levels of IFN-γ (p<0.05) and TNFα (p<0.05) synthesis when compared to NOD-Ncf1µ or ALR splenocytes. In contrast, activated NOD-Ncf1µ and ALR splenocytes secreted a cytokine profile indicative of a Th17 response as observed by higher levels of IL-17 (p<0.01) and IL-10 (p<0.05) in comparison to NOD splenocytes. In conclusion, inhibition of NOX is protective against T1D and inhibition of immune cell O2• appears to skew immune responses away from a pathogenic Th1 and towards a potentially non-pathogenic Th17 response. These results also support a role for 02• production in polarizing an immune response. [ABSTRACT FROM AUTHOR]