A decreased expression of PD-L1 on myeloid cells in systemic JIA (sJIA) patients, compared with patients with febrile disease of other aetiologies, has been observed.10 A subsequent study reported reduced numbers of circulating peripheral blood CD4+ T-cells with reduced PD-1 expression in sJIA patients, compared to healthy controls and patients with polyarticular disease, or enthesitis-related arthritis. This evidence concerns the gene PDCD1 and systemic-onset juvenile idiopathic arthritis.