The beneficial therapeutic effect of the anti-IL-17 antibody ixekizumab and the anti-IL-17 receptor antibody brodalumab in psoriasis, psoriatic arthritis, ankylosing spondylitis, and refractory RA is further evidence for the involvement of Th17 cells in these disorders [19–23]. This evidence concerns the gene IL17A and ankylosing spondylitis.