TNF and rheumatoid arthritis: Accumulating research indicate that FLSs play vital role in RA by producing proinflammatory cytokines, such as interleukin (IL)-6, IL-1β, tumor necrosis factor (TNF)-α, inducible nitric oxide synthase (iNOS), and proteinases, such as matrix metalloproteinases (MMPs), which perpetuate joint destruction3,5.