TNF and rheumatoid arthritis: In RA, inflammatory cytokines, such as interleukin (IL)-6 and tumor necrosis factor-alpha (TNF-α), cause dysregulated proliferation and drive a migratory and invasive phenotype of synovial fibroblast [6,7] (also known as fibroblast-like synoviocytes (FLS)) [8], resulting in pannus formation.