IL-22 is a cytokine structurally related to IL-10. Mouse IL-22 consists of 179 amino acids and has a predicted molecular weight of 20 kD. It is secreted primarily by Th17, Th1, Th2, lymphoid tissue inducer cells (LTi), and subsets of natural killer cells. It has been reported that aryl hydrocarbon receptor (AhR) expression is essential for the production of IL-22 by TCRgammadelta T cells. AhR activation increases Th17 polarization and induces IL-22 production. IL-22 functions by engaging the heterodimeric IL-22 receptor (IL-22R) complex, consisting of two receptor subunits, IL-22R1 and IL-10Rbeta. IL-22 acts on nonhematopoietic tissue cells, such as epithelial cells of the digestive and respiratory systems and karatinocytes of the skin. IL-22 is involved in inflammatory processes such as dermal inflammation, psoriasis, inflammatory bowel disease, hepatitis, and crohn’s disease. Moreover, it plays a critical role in mucosal immunity and wound healing process.