Other studies suggested that Th17 that can produce IL-17A and IFN-γ at the same time were pathogenic Th17, which were the main infiltrating CD4+ T cells in several inflammatory diseases (such as rheumatoid arthritis, psoriasis, Crohn's disease, and MS) and could exacerbate these diseases development [20, 21]. This evidence concerns the gene IL17A and psoriasis.