IL-22 is a member of the IL-10 family of regulatory cytokines which includes IL-10, IL-19, IL-20, IL-22, IL-24 and IL-26. Members of this family share partial homology in their amino acid sequences, but they are dissimilar in their biological functions. IL-22 is produced by activated dendritic cells and T lymphocytes. IL-22 signals through a receptor system consisting of IL-10R-beta, CRF2-4 and IL-22R.