Fibrinogen is a plasma clotting factor composed of three different polypeptide chains (, and ). Under chronic inflammatory conditions, fibrinogen can be acted upon by the peptidylarginine deiminases enzymes (PAD2 and PAD4), converting specific arginine residues to citrulline. Patients with rheumatoid arthritis (RA) produce antibodies that bind citrullinated human fibrinogen.1 The citrullinated fibrinogen and rEActive antibodies form immune complexes in RA patients, and these immune complexes can stimulate macrophages.2,3 Immunizing certain strains of mice with citrullinated human fibrinogen can induce the production of anti-citrullinated human fibrinogen antibodies and the development of arthritis that shares many pathophysiological fEAtures of the human disEAse.4,5Technical InformationPurityHomogeneous by SDS-PAGE. Clottable proteins: 95%SourceFibrinogen, purified from human plasma that has been shown by certified tests to be negative for HBsAg and for antibodies to HIV and HCV. Citrullinated with human recombinant PAD2.MWUncitrullinated fibrinogen: chain isoform 1 (95 kDa), chain isoform 2 (69.8 kDa), chain (55.9 kDa) and isoform -B chain (51.5 kDa)FormulationA lyophilized powder