Anti-cyclic citrullinated peptide antibodies are a collection of anti-citrullinated protein antibodies and contain overlapping and non-overlapping reactivities. Issue 1 (24th August 2010)

• Record Type: Journal Article
• Authors: Ioan-Facsinay, Andreea; el-Bannoudi, Hanane; Scherer, Hans U; van der Woude, Diane; Ménard, Henri A; Lora, Maximilien; Trouw, Leendert A; Huizinga, Tom W J; Toes, Rene E M
• Is Part Of: Annals of the rheumatic diseases. Volume 70:Issue 1(2011)
• Page Start: 188
• Page End: 193
• Publication Date: 2010-08-24
• Subjects: Rheumatism -- Periodicals; 616.723005
• DOI: 10.1136/ard.2010.131102
• Languages: English
• ISSNs: 0003-4967

Abstract

Abstract : Objective: Anti-citrullinated protein antibodies (ACPA) and anti-cyclic citrullinated peptide (anti-CCP) antibodies are a hallmark of rheumatoid arthritis and are believed to play a role in disease pathogenesis. These antibodies are typically detected in ELISA with citrullinated peptides (eg, CCP2) or proteins as antigens. The absolute concentration of anti-CCP antibodies in serum is unknown. Although antibodies to several citrullinated proteins can mainly be detected within anti-CCP-positive sera, it is currently unknown whether anti-CCP antibodies are in fact ACPA. Likewise, it is unknown to what extent antibody responses to different citrullinated antigens are crossreactive. Methods: An affinity purification method was established in which citrullinated antigen-specific antibodies were eluted from ELISA plates and then used for detection of other citrullinated antigens in ELISA or western blot. For additional crossreactivity studies, ELISA-based inhibition assays were performed with citrullinated or control peptides as inhibitors. Results: The concentration of anti-CCP IgG antibodies was estimated to be at least 30 μg/ml in patients with high anti-CCP levels (>1600 μg/ml). Affinity-purified anti-CCP antibodies were able to recognise citrullinated fibrinogen (cit-fib) and citrullinated myelin basic protein (cit-MBP) on western blot. Furthermore, antibodies specific for cit-fib and cit-MBP were crossreactive. However, additional crossreactivity studies indicated that non-overlapping antibody responses to citrullinated peptides can also exist in patients. Conclusions: This report shows for the first time that anti-CCP antibodies recognise multiple citrullinated proteins and are thus a collection of ACPA. More importantly, the data indicate that different ACPA responses are crossreactive, but that crossreactivity is not complete, as distinct non-crossreactive responses can also be detected in patients with RA.