Anti-cyclic citrullinated peptide (anti-CCP) antibodies are autoantibodies directed against peptides and proteins that are citrullinated. Citrullination is a post-translational modification of the amino acid arginine into citrulline by the enzyme peptidylarginine deiminase (PAD). The presence of anti-CCP antibodies is highly specific for diagnosing rheumatoid arthritis (RA).
