Cutting edge: regulation of intestinal inflammation and barrier function by IL-17C.

In the IL-17 family of cytokines, much is known about the sources and functions of IL-17, IL-17F, and IL-25 in the host defense against infection and in inflammatory diseases; however, the physiological function of IL-17C remains poorly understood. Using mice deficient in IL-17C, we demonstrate that this cytokine is crucial for the regulation of an acute experimental colitis elicited by dextran sulfate sodium. In this model, mice lacking IL-17C exhibited exacerbated disease that was associated with increased IL-17 expression by γδ T cells and Th17 cells. Moreover, IL-17C directly regulated the expression of the tight junction molecule occludin by colonic epithelial cells. Thus, our data suggest that IL-17C plays a critical role in maintaining mucosal barrier integrity.