Innate lymphoid cells drive interleukin-23-dependent innate intestinal pathology

Abstract

The key role of IL-23 in the pathogenesis of autoimmune and chronic inflammatory disorders is supported by the identification of IL-23R susceptibility alleles associated with IBD, psoriasis and ankylosing spondylitis. IL-23 driven inflammation has primarily been linked to the actions of Th17 cells1. Somewhat overlooked, IL-23 also has inflammatory effects on innate immune cells2 and can drive T cell- independent colitis. However the downstream cellular and molecular pathways involved in this innate intestinal inflammatory response are poorly characterized. Here we show that bacteria-driven innate colitis is associated with increased IL-17 and IFN-γ production in the colon. Stimulation of colonic leukocytes with IL-23 induced IL-17 and IFN-γ production exclusively by innate lymphoid cells expressing Thy1, SCA-1, RORγt and IL-23R and these cells markedly accumulated in the inflamed colon. Importantly, IL-23 responsive innate intestinal cells are also a feature of T-cell dependent models of colitis. The transcription factor RORγt, which controls IL-23R expression, plays a functional role as Ror−/−Rag−/− mice failed to develop innate colitis. Lastly, depletion of Thy1+ innate lymphoid cells completely abrogated acute and chronic innate colitis. These results identify a novel IL-23 responsive innate lymphoid population that mediates intestinal immune pathology and may therefore represent a target in IBD.