PDCD1 and juvenile idiopathic arthritis: In fact, previous studies have demonstrated that JIA patients have a predominant Th17 cells’ phenotype not only in circulation, but also in joints, which has been associated with JIA pathophysiology and reinforces a Th17 polarisation environment.57 Indeed, a Th17/Treg cell imbalance has been suggested as a contributor to JIA pathogenesis.46 58 59 Furthermore, lower levels of PD1+Tfh cells, PD1+ICOS+Tfh cells and Tph cells were found in JIA patients when compared with controls.