IL-22 (human):Fc (human) (rec.)

The IL-22 gene includes five exons and a 537 bp-long open reading frame that encodes for a 179 amino acid protein. IL-22 is a member of the interleukin-10 (IL-10) family of cytokines which includes nine members, IL-10; the IL-20 subfamily members IL-19, IL-20, IL-22, IL-24, and IL-26; and the distantly related cytokines IL-28A, IL-28B, and IL-29, which are more commonly classified as type III interferons (IFNs) and designated as IFN-λ2, IFN-λ3, and IFN-λ1. Mouse and human IL-22 share 79% homology.  IL-22 is mainly produced by lymphocytes, such as T helper type 1 (Th1), Th17, Th22, CD8⁺ T cells, γδT cells, natural killer cells, lymphoid tissue inducer cells, innate lymphoid type 3 (ILC3) cells, and also by neutrophils. IL-22 has two heterodimeric transmembrane receptors, IL-22R1 and IL-10R2, which subsequently activate the JAK/STAT3, ERK and JNK pathways.

IL-22 responsiveness is limited by epithelial cell-restricted expression of IL-22RA1 in the lung, gastrointestinal tract, thymus, skin, pancreas, liver and kidney and represents a major communication channel between the immune system and specialized tissue cell types. IL-22 is a critical regulator of epithelial homeostasis, implicated in multiple aspects of epithelial barrier function, including regulation of epithelial cell growth and permeability, production of mucus and antimicrobial proteins (AMPs) and complement production. IL-22 plays key functions in the intestine and, therefore, plays a protective role in inflammatory bowel disease (IBD). IL-22 is also a controversial cytokine in tumor development; the IL-22-STAT3 axis induces anti-apoptotic genes and provides survival and proliferation signals for both normal and malignant cells. Therefore, in healthy conditions, it prevents tumor formation; however, once a tumor has been established, IL-22 promotes tumorigenesis.