IL-10 engages macrophages to shift Th17 cytokine dependency and pathogenicity during T cell-mediated colitis

Polymorphisms attenuating IL-10 signaling confer genetic risk for inflammatory bowel disease. Yet how IL-10 prevents mucosal autoinflammation is incompletely understood. We demonstrate using lineage-specific deletions of IL-10Rα that IL-10 acts primarily through macrophages to limit colitis. Colitis depends on IL-6 to support pathologic Th17 cell generation in wild type mice. However, specific ablation of macrophage IL-10Rα provokes excessive IL-1β production that overrides Th17 IL-6 dependence, amplifying the colonic Th17 response and disease severity. IL-10 not only inhibits pro-IL-1β production transcriptionally in macrophages, but suppresses caspase-1 activation and caspase-1 dependent maturation of pro-IL-1β to IL-1β. Therefore lineage-specific effects of IL-10 skew the cytokine dependency of Th17 development required for colitis pathogenesis. Coordinated interventions may be needed to fully suppress Th17-mediated immunopathology.