The importance of TH17 cells in these processes was suggested first in animal models of these diseases, including experimental autoimmune encephalomyelitis, and an IL-23– or imiquimod-induced psoriasis model,5, 6, 7, 8, 9 and was validated recently by clinical effectiveness of antibodies targeting IL-23 in patients with psoriasis.10, 11, 12, 13, 14. This evidence concerns the gene IL23A and experimental autoimmune encephalomyelitis.