We hypothesized that quercetin has an anti-inflammatory effect and an additive effect when combined with UCMSCs, and this study aimed to investigate the mechanism by which quercetin and UCMSCs affect TNF-α and IFN-γ-stimulated PBMCs and explain the effect of quercetin and UCMSC treatment on clinical symptoms and disease activity in patients with RA. Here, IFNG is linked to rheumatoid arthritis.