Figure 1.

Complex role of smoking in the pathogenesis of rheumatoid arthritis. ACPA, anti-citrullinated protein antibody; AP-1, activator protein-1; EBV, Epstein–Barr virus; HQ, hydroquinone; IRF-5, interferon regulatory factor 5; nACh, nicotinic acetylcholine; PAD, peptidyl arginine deiminase; PADI4, gene of peptidyl arginine deiminase type 4; PTPN22, protein tyrosine phosphatase nonreceptor 22; RA, rheumatoid arthritis; RF, rheumatoid factor; SE, shared epitope.