IL17A and psoriasis: In the early stage of psoriasis, after being activated by various external factors, dendritic cells and keratinocytes start to show innate immune response through the secretion of innate immune molecules such as AMP (Mahil et al., 2016) and then induce the activation of T cells in the skin to secrete pro-inflammatory factors such as IL-17 and IL-22 (Cai et al., 2011).