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Anti–citrullinated protein antibodies (ACPAs) are autoantibodies (antibodies directed against an individual’s own proteins) that are directed against peptides and proteins that are citrullinated. They are present in the majority of patients with rheumatoid arthritis. Clinically, cyclic citrullinated peptides (CCP) are frequently used to detect these antibodies with high sensitivity in patient serum or plasma (then referred to as anti–citrullinated peptide antibodies). One of the first identified antigens for these antibodies is citrullinated filaggrin. Historically, the same antibody specificity has been described as anti-keratin antibodies (AKA) and anti-perinuclear factor (APF). During inflammation, arginine amino acid residues can be enzymatically converted into citrulline ones in proteins such as vimentin, a process called citrullination. If their shapes are significantly altered, the proteins may be seen as antigens by the immune system, thereby generating an immune response. ACPAs have proved to be powerful biomarkers that allow the diagnosis of rheumatoid arthritis (RA) to be made at a very early stage. In July 2010, the ''2010 ACR/EULAR Rheumatoid Arthritis Classification Criteria'' were introduced. These new classification criteria include ACPA testing, and overruled the "old" ACR criteria of 1987 and are adapted for early RA diagnosis. ==History== The presence of autoantibodies against citrullinated proteins in rheumatoid arthritis patients was first described in the mid-1970s when the biochemical basis of antibody reactivity against keratin and filaggrin was investigated. Subsequent studies demonstrated that autoantibodies from RA patients react with a series of different citrullinated antigens, including fibrinogen, deiminated Epstein-Barr Virus Nuclear Antigen 1 and vimentin, which is a member of the intermediate filament family of proteins. Several assays for detecting ACPAs were developed in the following years, employing mutated citrullinated Vimentin (MCV-assay), filaggrin-derived peptides (CCP-assay) and viral citrullinated peptides (VCP-assay). In 2010, ACPA testing has become substantial part of ''The 2010 ACR-EULAR classification criteria for rheumatoid arthritis''. 〔 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「Anti–citrullinated protein antibody」の詳細全文を読む スポンサード リンク
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