TNF and rheumatoid arthritis: The fibroblast-like synoviocytes (FLSs), located in the synovium, mediate synovial joint destruction by releasing metalloproteinases (MMPs) and secreting cytokines, including interleukin (IL)-6, IL-Iβ, IL-8, and tumour necrosis factor (TNF)-α in RA.2–6