TNF-α plays a key role in the pathogenesis of many inflammatory diseases; it has been detected in all tissues affected by active inflammation, such as the synovial fluid in patients with rheumatoid arthritis (RA) or psoriasis arthritis (PsA), the bowel mucosa in Crohn’s disease or ulcerative colitis, and the eye during acute uveitis. The gene discussed is TNF; the disease is rheumatoid arthritis.