IL17A and psoriasis: Subcutaneous injection of IL‐23, together with IL‐12 and TNF produced by LCs and DCs, activates αβT and γδT cells to produce IL‐22 and IL‐17A/F, which stimulate keratinocyte proliferation, release S100 protein and β‐defensin, and promote the production of growth factors and chemokines in psoriasis.100