Interleukin‐22 and intestinal homeostasis: Protective or destructive?

Interleukin (IL)‐22 is a member of IL‐10 family cytokines with various immunologic functions. As its name implies, IL‐22 is known to be secreted mainly by Th22 cells, a recently discovered lineage of CD4+ T cells. Also, Th17, Th1, natural killer cells, γδT cells, and innate immune cells along with some nonlymphoid cells have been confirmed as secondary cellular sources of IL‐22. Different cell types such as bronchial and intestinal epithelial cells, keratinocytes, hepatocytes, dermal fibroblasts, and tubular epithelial cells are affected by IL‐22. Both pathologic and protective roles have been attributed to IL‐22 in maintaining gut homeostasis and inflammation. According to the latest fast‐growing investigations, IL‐22 is significantly involved in various pathologies including allergic diseases, infection, autoimmunity, and cancer development. Regulating gut immune responses, barrier integrity, and inflammation is dependent on a diverse complex of cytokines and mediators which are secreted by mucosal immune cells. Several investigations have been designed to recognize the role of IL‐22 in gastrointestinal immunity. This article tries to discuss the latest knowledge on this issue and clarify the potential of IL‐22 to be used in the future therapeutic approaches of intestinal disorders including inflammatory bowel diseases and colon cancer. [ABSTRACT FROM AUTHOR]