Many cytokines contribute to RA (IFN-γ, IL-12, IL-21, and IL-23) but the primary cytokines are IL-6, which promotes synovial inflammation, cartilage, and bone destruction; TNF-α, which when dysregulated in experimental animals, is sufficient to cause destructive arthritis and; IL-1, which stimulates synoviocytes and chondrocytes. Here, TNF is linked to rheumatoid arthritis.