Interleukin-23 (IL23) is a heterodimer of Interleukin-12 subunit beta (IL12B, IL-12p40), which is shared with IL12, and Interleukin-23 subunit alpha IL23A (IL-23p19) subunit. The functional receptor for IL23 consists of Interleukin-12 receptor subunit beta-1 (IL12RB1), which is shared with the IL12 receptor, and Interleukin-23 receptor (IL23R). IL23R is mainly expresed on activated memory T cells, Natural Killer cells, monocytes/macrophage and at low levels on dendritic cells (DCs). IL23 is mainly secreted by activated macrophages and DCs in peripheral tissues such as skin, intestinal mucosa and lung.
IL23 is proinlflammatory and implicated in several autoimmune inflammatory disorders such as colitis, gastritis, psoriasis and arthritis. It is similar to IL-12 both in structure and its ability to memory T cells to increase interferon-γ (IFN-γ) production and proliferation, the ability of IL-23 to induce IL-17.
IL23 activates the Janus kinases JAK2 and TYK2, resulting in phosphorylation of the receptor complex, which forms the docking sites for Signal transducer and activator of transcription 3 (STAT3) and STAT4 to bind and become phosphorylated.