Macrophages are one of the principal drivers of both inflammation and chronicity in the joint of RA patients where they secrete many of the factors closely associated with this disease; pro-inflammatory cytokines (TNF-α, IL-1 and IL-6), chemoattractants (CCL2 and IL-8) as well as tissue remodeling enzymes (MMP-3 and MMP-12) (44). Here, CCL2 is linked to rheumatoid arthritis.