We first tested four JAK inhibitors of different reported specificity (see Supplementary Table S1) for their ability to inhibit secretion of IL-17A from purified blood CD4+ T cells cultured for 3 days in an initial cohort of 43 Ankylosing Spondylitis (AS), 16 Psoriatic Arthritis (PSA), 18 Rheumatoid Arthritis (RA) patients and 26 healthy controls (HC). This evidence concerns the gene CD4 and psoriatic arthritis.