Which statement best describes anti-CCP antibodies?

• A. They are IgG antibodies that attack citrullination-altered shapes
• B. They are IgM antibodies that target citrullinated proteins
• C. They are autoantibodies that target DNA
• D. They are antibodies that neutralize inflammatory cytokines

Answer: (A)

Anti-CCP antibodies are autoantibodies directed against citrullinated peptides, which are proteins that have undergone citrullination, a post-translational modification that creates new peptide shapes (neoepitopes). In rheumatoid arthritis, the most clinically useful tests detect IgG autoantibodies against cyclic citrullinated peptide sequences; this IgG class is typically what is measured and provides high specificity for RA. This makes the description that they are IgG antibodies that recognize citrullination-altered shapes the best choice. They are not autoantibodies against DNA, nor antibodies that neutralize inflammatory cytokines, and while other isotypes can exist, the standard anti-CCP test centers on IgG.