IL17A and psoriasis: In psoriasis, epidermal keratinocytes express KRT17, which may be recognized by DCs to trigger their own activation and maturation; mature DCs further secrete inflammatory factors and induce immature T cells to differentiate into Th1 and Th17 cells, which produce large amounts of IL-17 and IL-22 to induce epidermal keratinocyte proliferation [33,34].