The migration and infiltration of monocytes to lesions of inflammatory is mediated by inflammatory/inducible cytokines that are preferentially produced in peripheral tissue at those sites; c-c motif chemokine ligand 2 (CCL2, also known as monocyte chemoattractant protein-1 [MCP-1]) is particularly important for its chemotactic activities in RA 7. The gene discussed is CCL2; the disease is rheumatoid arthritis.