CSF2 and rheumatoid arthritis: Macrophages are the major source of pro-inflammatory cytokines and chemokines in the inflamed RA joint, including tumour necrosis factor (TNF), interleukin-1 (IL-1), interleukin-8 (IL-8) and granulocyte-macrophage colony-stimulating factor (GM-CSF) [15], [19].