One proposed mechanism is the presence of sPD1 which blocks the PD1 pathway by antagonistically binding to the membrane-bound PD1’s ligands.10 This hypothesis is supported by the majority of studies in RA, which have demonstrated high serum and SF sPD1 levels, especially in active disease.23,26–29 There are very few data in the literature regarding sPD1 in JIA and they are centred in specific JIA subtypes. The gene discussed is PDCD1; the disease is juvenile idiopathic arthritis.