CCL2 and rheumatoid arthritis: MCP-1/CCL2 [13], Gro-α/CXCL1 [16], ENA-78/CXCL5 [15], and IL-8/CXCL8 levels are elevated in RA synovial fluid and serum compared with osteoarthritic synovial fluid and normal peripheral blood levels [15].