TNF and rheumatoid arthritis: We searched the PubMed database for sources using the following keywords: the pathogenesis of rheumatoid arthritis; rheumatoid arthritis and proinflammatory cytokines; proinflammatory cytokines and autoimmune diseases; the biology of IL-1, -6, -8, - 12, -15, -17, -18, -23, TNF-α; rheumatoid arthritis and IL-1, -6, -8, -12, -15, -17, -18, -23, TNF-α; rheumatoid arthritis and single nucleotide polymorphisms of IL-1, -6, -8, -12, -15, -17, -18, -23, TNF-α; rheumatoid arthritis and SNPs of IL-1, -6, -8, -12, -15, -17, -18, -23, TNF-α.