Th1 secretes interferon (IFN)-γ to activate macrophages, and Th17 secretes IL-17A/F and IL-22; recruits neutrophils; induces synovial fibroblasts to produce granulocyte–macrophage colony-stimulating factor (GM-CSF) and IL-6; and promotes RA inflammation amplification and pain exacerbation (44, 45). This evidence concerns the gene IL17A and rheumatoid arthritis.