IL17A and psoriasis: These studies suggest, in common, that interactive reaction between immune cells in the skin, such as keratinocytes, T helper cell 1 (Th1), Th17, Th22, neutrophils, and mast cells, along with the abnormal expression of cytokines such as interferon alpha (IFN-a), tumor necrosis factor alpha (TNF-a), IL-17, IL-22, and IL-23; are mainly implicated in the occurrence of psoriasis [20,21].