CXCL8 and rheumatoid arthritis: MIF stimulates release of the proinflammatory cytokines TNF-α, IL-1, IL-6, IL-8, and IL-12 from macrophages and up-regulates matrix metalloproteinase (MMP) -1, MMP-3, MMP-9 and MMP-13 in RA FLS [16, 51–57].