IL-23p19 associates with IL-12b to form the IL-23 interleukin, an heterodimeric cytokine which functions in innate and adaptive immunity. IL-23 binds to an heterodimeric receptor complex composed of IL-12RB1 and IL-23R, activates the Jak-Stat signaling cascade, stimulates memory rather than naive T-cells and promotes production of proinflammatory cytokines. IL-23 induces autoimmune inflammation and thus may be responsible for autoimmune inflammatory diseases and may be important for tumorigenesis.