IL-22 is a member of IL-10 superfamily. It is produced by Th17 cells and NK cells, especially in epithelial cells. Human IL-22 cDNA encodes a 179 amino acid (aa) residue protein with a putative 33 aa signal peptide that is cleaved to generate a 147 aa mature protein. Mouse IL-22 shares 79% similarity to human IL-22. IL-22 binds to a receptor complex consisting of IL-22 R and IL-10 R beta. IL-22 and IL-10 receptor chains play a role in cellular targeting and signal transduction to selectively initiate and regulate immune responses. IL-22 can contribute to immune disease through the stimulation of inflammatory responses. IL-22 also promotes hepatocyte survival in the liver and epithelial cells in the lung and gut similar to IL-10.