CCL2 and rheumatoid arthritis: In RA patients, M1 macrophages secret more TNF‐α and IL‐1, while M2 macrophages secret less IL‐10 than those in healthy people.[65] Macrophages also produce reactive oxygen species (ROS), including C‐X‐C chemokine ligand 8 (CXCL8) and CCL2, to promote the progression of RA.