The core pathogenesis of psoriasis involves aberrant function of multiple T-cell subsets, including regulatory T cells (Tregs), T helper (Th)1 cells, Th2 cells, Th17 cells, and Th22 cells, accompanied by aberrant release of associated cytokines, such as IFN-γ, tumor necrosis factor (TNF)-α, and members of the IL-23 and IL-17 families (45). This evidence concerns the gene IL17A and psoriasis.