IL17A and psoriasis: Psoriasis is a skin-specific, immune-mediated disease that seriously endangers human health.1 It affects approximately 2% of the population in Europe and North America, and there are more than 6 million psoriasis patients in China.2,3 The pathogenesis is mainly mediated by dendritic cells (DCs), T cells, and keratinocytes.4 Among them, Th17 cells play an important role in the occurrence and development of psoriasis by producing IL-17A, which stimulates several responses that promote keratinocyte hyperproliferation, epidermal hyperplasia, and skin inflammation.5,6