IL23R, also known as the IL23 receptor, belongs to the type I cytokine receptor family, Type 2 subfamily. It contains 2 fibronectin type-III domains and is expressed by monocytes, Th1, Th0, NK, and dendritic cells. Isoform 1 is specifically expressed in NK cells. IL23R associates with IL12RB1 to form the interleukin-23 receptor. It binds IL23 and mediates T-cells, NK cells, and possibly certain macrophage/myeloid cell stimulation probably through activation of the Jak-Stat signaling cascade. IL23 functions in innate and adaptive immunity and may participate in acute response to infection in peripheral tissues. IL23 may be responsible for autoimmune inflammatory diseases and be important for tumorigenesis. Genetic variations in IL23R are associated with inflammatory bowel disease type 17 (IBD17). IBD17 is a chronic, relapsing inflammation of the gastrointestinal tract with a complex etiology. Genetic variations in IL23R also can cause susceptibility to psoriasis type 7.