IL17A and psoriasis: Previous studies revealed that the pathological process of psoriasis is closely associated with the expression of certain pertinent genes involved in the expression of genes encoding cytokines and vascular endothelial growth factors, such as TNF-α, IL-22, IL-17A, etc. For example, the major cytokine associated with keratinocyte hyperproliferation observed in psoriasis is strongly associated with IL-22 production by cutaneous c-Kit + FC-εRI + mast cells and Th17, Th22, and Tc22 cells (CD8 + T cells).