IL-22 plays an indispensable role in early host defense against attaching and effacing (A/E) bacterial pathogens

Infection by attaching and effacing (A/E) pathogens poses a serious threat to public health, as was highlighted by the recent outbreak of E. coli O157:H7 infection in the United States. Here, by using a murine A/E pathogen, Citrobacter rodentium, we demonstrate that C. rodentium infection is lethal to IL-22-/- mice within two weeks. IL-22, in the early phase of infection, is indispensable for preventing the invasion of bacteria through the intestinal epithelium, and thereby preventing systemic spread and mortality. We also show that IL-23 is required for the early induction of IL-22 during C. rodentium infection. Finally, our data suggest that IL-22 exerts its function by boosting the innate immune responses of colonic epithelial cells, especially though the induction of anti-microbial proteins, RegIIIβ and RegIIIγ. Keywords: treatment comparison Control or IL-22-treated mouse colon in triplicate.