FN1 and rheumatoid arthritis: Indeed, autoimmune arthritis was induced by administrating citrullinated type II collagen (CII) in the absence of adjuvant,10 whereas immunization using citrullinated fibrinogen led to inflammatory arthritis in HLA-DR4 transgenic mice.11 Citrullinated proteins known to be associated with RA include fibrin,12 vimentin,13 fibronectin,8 anti-immunoglobulin binding protein (BiP)14 and CII.15