IL22 is a key regulator of immunity and inflammation at the mucosal surface. It is produced by cells from the innate and adaptive immune system, like ILCs, γδT-cells, NK, TH1,17&22 cells. The latter are together with ILC3s the main source of IL-22. IL-22 is considered as a non-inflammatory cytokine and show similarities with IL-10. ILC3s are present in large numbers in mucosal layers and do not require antigen recognition for their activation. In barrier organs the mucosal layer is constantly in contact with the environment and needs to adapt to this continuously trigger by microbes and their metabolites in order to prevent acute inflammation. Thereby IL-22 has important functions in host defense and tissue repair. IL-22 provides protective innate immunity in the absence of an adaptive response. IL-22 signals via heterodimeric receptor complex (IL-22R1&2) expressed on epithelial cells of the lung, gut, skin, liver, pancreas and kidneys. It is not expressed by hematopoietic cells. Another mechanism of IL-22 to control pathogens is by aiding the binding of complement C3 to the bacteria. Furthermore IL22 increases C3 expression in the liver. IL-22 binding protein exists in humans as a soluble form of IL-22 receptor. Binding to the receptor results primarily in JAK/STAT downstream signaling IL-22 induces expression of chemokines like CXCL1&5 and stimulates the expression of antimicrobial peptides such as beta-defensins, S100 peptides and calprotectin. Elevated levels of this IL-22 has been seen in chronic inflammatory diseases such as psoriasis, rheumatoid arthritis and some lung diseases. The antibody is cross reactive to mouse and rat IL-22.