IL22 is a member of a group of cytokines called the IL-1 family or IL-1 superfamily (including IL-19, IL-2, IL-24, and IL-26), a class of potent mediators of cellular inflammatory responses. It shares use of IL-1R2 in cell signaling with other members of this family, IL-1, IL-26, IL-28A/B and IL-29. IL22 is produced by activated DC and T cells and initiates innate immune responses against bacterial pathogens especially in epithelial cells such as respiratory and gut epithelial cells. IL22 along with IL-17 is rapidly produced by splenic LTi-like cells and can be also produced by Th17 cells and likely plays a role in the coordinated response of both adaptive and innate immune systems. IL22 biological activity is initiated by binding to a cell-surface complex composed of IL-22R1 and IL-1R2 receptor chains and further regulated by interactions with a soluble binding protein, IL-22BP, which shares sequence similarity with an extracellular region of IL-22R1 (sIL-22R1). IL22 and IL-1 receptor chains play a role in cellular targeting and signal transduction to selectively initiate and regulate immune responses. IL22 can contribute to immune disease through the stimulation of inflammatory responses, S1s and defensins. IL22 also promotes hepatocyte survival in the liver and epithelial cells in the lung and gut similar to IL-1. In some contexts, the pro-inflammatory versus tissue-protective functions of IL22 are regulated by the often co-expressed cytokine IL-17A.
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