IL-23

Interleukin-23 (IL-23) is a heterodimeric cytokine composed of a unique p19 subunit (IL-23α) paired with the p40 subunit (IL-12B) shared with IL-12. Secreted mainly by activated dendritic cells and macrophages, IL-23 signals through IL-23R and IL-12Rβ1, activating JAK2/TYK2-STAT3 and STAT4. Rather than inducing Th1 differentiation like IL-12, IL-23 is the key maintenance and stabilization factor for Th17 cells and IL-17-producing γδ T cells and group 3 innate lymphoid cells, sustaining IL-17A, IL-17F, IL-22 and GM-CSF production. This axis underlies autoimmune and chronic inflammatory pathology in psoriasis, psoriatic arthritis, ankylosing spondylitis, Crohn's disease and multiple sclerosis. Ustekinumab (anti-p40), risankizumab and guselkumab (anti-p19) demonstrate the clinical power of blocking IL-23 in these diseases.