CD25brightCD4+ T cell population persists over time. (a) Eight patients with psoriatic arthritis (PsA), (b) four patients with spondyloarthopathies (SpA) and (c) eight patients with juvenile idiopathic arthritis (JIA) were followed longitudinally, and the frequency of synovial CD25brightCD4+ T cells was measured at each relapse from which synovial fluid was obtained. Open symbols depict patients who had two relapses during the study period; filled symbols depict patients who had three or more relapses. Time point zero corresponds to the first time point at which synovial fluid was analyzed for the frequency of CD25brightCD4+ T cells. From one patient with PsA and one with SpA, samples from both knees were obtained; arrows pointing left, left knee; arrows pointing right, right knee.