On the one way, IL-17A directly induces IL-19 and IL-24 expression of fibroblast cells in the skin via binding with IL-17RA and IL-17RC, which further contributes to keratinocyte proliferation and acanthosis.69 On the other way, the released IL-17A also acts on other immune cells to facilitate psoriasis pathogenesis. This evidence concerns the gene IL17A and psoriasis.