TNF plays a central role in initiation and promotion of inflammation (Old, 1985; Körner and Sedgwick, 1996; Sedgwick et al., 2000), thus dysregulated TNF production and function are associated with the pathogenesis of inflammatory diseases such as rheumatoid arthritis (RA), inflammatory bowel disease, systemic lupus erythematosus, ankylosing spondylitis, and multiple sclerosis (Kollias et al., 1999; Kollias, 2005). Here, TNF is linked to rheumatoid arthritis.