CLDN1 and colitis: Whether the induction of this population by IL-17 solely explains all of the protective function of IL-17 in colitis remains arguable, since we also observed that inflamed colonic tissue of IL-17KO mice expressed reduced levels of claudin-1/2, β-difensin-1/2, and mucin-2, all of which have been shown to be regulated by IL-17 signaling.