CCL2 and rheumatoid arthritis: RA is characterized by progressive inflammation with different elevated cytokines; IL-1, TNF-α, IL-6, granulocyte-macrophage colony-stimulating factor (GM-CSF), macrophage colony-stimulating factor (M-CSF), transforming growth factor-beta (TGF-β), and chemokines; monocyte chemoattractant protein-1 (MCP-1), macrophage inhibitory protein-1 (MIP-1), and epithelial-neutrophil activating peptide (ENA) (7).