KDR and rheumatoid arthritis: Prior research investigated the impact of IL-35 on VEGF (vascular endothelial growth factor) and its receptors, Flk-1 and Flt-1, in a collagen-induced arthritic mice model of rheumatoid arthritis revealed that the IL-35 therapy decreased levels of TNF-α and other indicators, including VEGF, Flt-1, and Flk-1 (Wu et al., 2016).