Interleukin-22 (IL-22) is a member of a group of cytokines called the IL-10 family which include IL-10,IL-19, IL-20, IL-24, and IL-26. IL-22 shares use of the IL-10R2 in cell signaling with other members of this family IL-22 signals through a receptor system consisting of IL-10R-β/CRF2-4 and IL-22R, both of which are members of the class II cytokine-receptor family. IL-22 is produced by activated DCs and T cells and initiates an innate immune response against bacterial pathogens especially in epithelial cells such as those in the respiratory tract and gut. IL-22 along with IL-17 is rapidly produced by splenic LTi-like cells and can also be produced by Th17 cells, which plays a likely role in the coordinated response of both adaptive and innate immune systems.