IL-23 is a heterodimeric cytokine composed of two subunits: a unique p19 subunit, and a p40 subunit that is shared with IL-12. IL-23 is secreted by activated dendritic cells and macrophages. IL-23 binds to a heterodimeric receptor complex composed of IL12RB1 and IL23R, activates the Jak-Stat signaling cascade, stimulates memory rather than naive T cells and promotes production of proinflammatory cytokines, such as IFNγ and IL-17. IL-23 induces autoimmune inflammation and thus may be resp