Anti-CCP: Anti–Cyclic Citrullinated Peptide Antibody
- Also known as Anti-Citrullinated Protein Antibody (ACPA)
- Useful in diagnosis and prognosis of rheumatoid arthritis (RA)
- Newest anti-CCP assay yields a specificity of 98%, the sensitivity of 80% for RA
- Present in 70% of patients with established RA
What is Anti-CCP?
- Anti-CCP antibodies are directed against citrullinated proteins
- Citrullination results from the post-translational modification (ie. not encoded in the original protein) of the amino acid arginine to citrulline by the enzyme peptidyl arginine deiminase
- Anti-CCP assays recognize a number of citrullinated proteins
Role of Anti-CCP
- Anti-CCP antibodies are used in the diagnosis and prognosis of RA
- Can be seen years prior to RA onset and rarely develop after onset, suggesting that they are not just a consequence of inflammation.
- Associated with a more severe disease course and a lower chance of drug-free remission.
Anti-CCP, HLA-DRB1 and the Shared Epitope
- A number alleles of the HLA-DRB1 locus cause a predisposition to Anti-CCP+ RA.
- HLA-DRB1 alleles encode one of the several 5 amino acid sequences that are grouped under the term Shared Epitope (SE). As part of the HLA molecule, the SE produces particular susceptibility to RA.
- Hypotheses include a role for the SE in T-cell repertoire selection or antigen presentation; molecular mimicry of the SE by microbial proteins; and a potential pro-inflammatory signalling function that is unrelated to the role of the SE in antigen recognition.
- The SE confers risk for more severe RA, as well as for the development of extra-articular manifestations.