CCL2 and rheumatoid arthritis: In addition, other inflammatory factors such as IL‐12, IL‐15, IL‐18, IL‐32, GM‐CSF, and chemokines such as IL‐8, monocyte chemoattractant protein‐1 (MCP‐1), and C‐X‐C motif ligand 13 (CXCL13), all contribute partially to RA.