Interleukin 23 receptor (IL23R) is a type I cytokine receptor for IL23. IL23 receptor complex is comprised of two subunits, the IL12Rβ1 subunit, which is shared with several cytokines, and a subunit that is unique to IL-23. IL23, after binding to IL23R, activates memory T cells and mediates pro-inflammatory activities in part by the production of IL17 through activation of TH17 lymphocytes. IL23R is expressed on T cells, NK cells, dendritic cells, and macrophages. In fact, polymorphisms of the IL23R gene were reported to be associated with susceptibility to inflammatory diseases and autoimmune diseases such as psoriasis, multiple sclerosis, Graves's ophtalmopathy and inflammatory bowel diseases. The IL23R is known to be critically involved in the carcinogenesis of different malignant tumor.