Similar to STAT6–/– mice, IL-5-deficient mice are protected from

Similar to STAT6–/– mice, IL-5-deficient mice are protected from allergic asthma [35], while monoclonal anti-IL-5 therapy attenuates airway disease successfully [36]. Therefore, it is likely that in crescentic GN, STAT6 activation results in IL-5 production which attenuates renal injury, possibly through the inhibition of Th1 and Th17 responses. Assessing renal injury early in the disease process at day 6 demonstrated no difference between WT and STAT6–/– mice. These results confirmed that the injury seen on day 21 was a result of the heightened systemic immunity which developed between days 6 and 21, and not a reflection of an existing predisposition to renal injury

in STAT6–/– mice. Interestingly, mRNA expression of both T-bet and Rorγt was increased in STAT6–/– mice, with a trend towards increased production of IFN-γ and IL-I7A on day 6. On day 21 differences in production of these cytokines by WT and STAT6–/– mice had reached statistical significance. Previous studies

in STAT6–/– mice in experimental lymphoproliferative disease demonstrated that STAT6 deficiency resulted in a shift from a predominant Th2 phenotype towards production of Th1-associated cytokines. In these experiments no difference was observed in the production of Th17-associated cytokines [37]. Consistent with these results, Th1 differentiation GPCR Compound high throughput screening occurred without the provision of extrinsic IFN-γ or IL-12 in conditional GATA3-deficient mice [38]. The ability of other key regulators to influence the associated and reciprocal Th cell lineages is well described. T-bet, the key regulator of Th1 responses, can influence the Th17 phenotype. In experimental allergic encephalomyelitis, inhibition of T-bet by small interfering RNA inhibited the production of both Th1 and Th17 pathogenic responses [39]. Conversely, it has been suggested that T-bet negatively N-acetylglucosamine-1-phosphate transferase regulates the production of Th17 associated cytokines in vitro[40]; this was demonstrated in vivo in experimental Chagas’ disease [41]. Taken together, these reports demonstrate that key Th1 transcription factors can influence the production of Th17 responses. We propose

that STAT6 influences pathogenic Th1 and Th17 inflammatory responses in experimental crescentic GN. This novel finding suggests a greater role for Th2 cells in experimental crescentic GN than was previously appreciated. In addition to IL-4 and IL-10, it would seem that STAT6 with IL-5 production is required for control of nephritogenic immunity. Production of the regulatory Th2-related cytokines is required not only for regulation of inflammatory Th1 responses but also for regulation of Th17 systemic immunity. In conclusion, we found that STAT6–/– mice developed increased expression of key Th1 and Th17 transcription factors early in the disease. This resulted in increased Th1 and Th17 nephritogenic immunity on day 21. Production of a key Th2-related cytokine, IL-5, was decreased consistently during the disease state.

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