CD4 and psoriasis: IL-23 acts on T cells, especially the CD4+ helper T cells (Th17 cells), via a cellular receptor complex comprising of two transmembrane proteins: IL-23Rα and IL-12Rβ1.52 Then, IL-23 promotes the release of interleukin-17 (IL-17), another critical cytokine involved in the pathogenesis of psoriasis, by Th17 cells through the activation of intracellular signals.53