CCL2 and rheumatoid arthritis: Our findings in fact support the literature data reporting that TNF-α-producing macrophages are the most abundant immune cells found in RA synovium, where they produce also other pro-inflammatory cytokines (IL-1β and IL-6), chemoattractant factors (CCL2 and IL-8), and metalloproteinases (MMP-3 and MMP-12) [61,62,63], inducing cellular proliferation and increased vascular permeability, which contribute to the pathogenic features of tissue proliferation and neovascularization characterizing rheumatoid synovium, along with cartilage and bone infiltration and destruction [63].