Similar to previous reports showing that administration of PD-L1-Fc can inhibit the development of collagen-induced arthritis (CIA) (54, 58), our results showing the effectiveness in PD-L1-Fc in ameliorating serum-induced arthritis in NOX2-deficient mice further support the critical role of PD-1/PD-L1 immune regulation in joint inflammation. This evidence concerns the gene CYBB and arthritic joint disease.