TNF and rheumatoid arthritis: Serum AA is produced in response to proinflammatory cytokines and messenger RNA of AA was found to be upregulated by TNF-α) and interleukin-1 (IL-1), as well as by IL-6 to a lesser extent, in fibroblast-like synoviocytes (FLSs) of patients with RA [19, 20].