IL-23

IL-23 is a member of the IL-12 family of cytokines. IL-23 is secreted by activated dendritic cells and activated macrophages, and functions in innate and adaptive immunity to regulate TH17 function and proliferation. It is an important signal mediator of TH17 differentiation and is thought to contribute to the functional deviation of TH17 cells. Additionally, IL-23 induces CD8+ memory T cells to proliferate and produce IL-17. As such, IL-23 has been described as a key cytokine controlling inflammation in peripheral tissues. Structurally, IL-23 is a heterodimeric cytokine composed of the p40, shared with IL-12, and p19, a subunit that belongs to the IL-6 superfamily of cytokines. IL-23 interacts with a heterodimeric receptor composed of IL-12Rβ1 and IL-23R that binds to JAK/STATs. Despite activating similar signaling pathways to IL-12, IL-23 binding can lead to weaker activation, especially with STAT4. Expression of IL-23R is linked to the development of Crohn’s disease in humans.