KEN OKAZAKI
Department School of Medicine(Tokyo Women's Medical University Hospital), School of Medicine Position Professor and Division head |
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Article types | Original article |
Language | English |
Peer review | Peer reviewed |
Title | Serum IgG ACPA-IgM RF immune complexes were detected in rheumatoid arthritis patients positive for IgM ACPA. |
Journal | Formal name:Clinical and experimental rheumatology Abbreviation:Clin Exp Rheumatol ISSN code:0392856X/0392856X |
Domestic / Foregin | Foregin |
Volume, Issue, Page | 36(4),pp.612-618 |
Author and coauthor | Haraguchi Akihisa†, Yamada Hisakata, Kondo Masakazu, Okazaki Ken, Fukushi Jun-Ichi, Oyamada Akiko, Yoshikai Yasunobu, Nakashima Yasuharu |
Publication date | 2018/07 |
Summary | OBJECTIVES:Since the presence of IgM antibodies is a hallmark of ongoing immune response, we aimed to identify immunologically active rheumatoid arthritis (RA) patients by detecting IgM anti-citrullinated protein antibody (ACPA) levels.METHODS:IgM ACPA levels were determined in the serum of 176 RA patients by enzyme-linked immunosorbent assay, in which parameters of reactivity against citrullinated and non-citrullinated peptides were compared to ensure the specificity. Influence of IgM rheumatoid factor (RF) on IgM ACPA detection was examined by removing IgG, using protein G-conjugated beads, or by purifying ACPA, using citrullinated peptide-conjugated beads.RESULTS:Although IgM specific for citrullinated proteins was detected in some patients (11%), IgM molecules reactive to both citrullinated and non-citrullinated peptides were detected in a substantial number of patient samples (12%). IgM ACPA-positive reactions were associated with the presence of IgG ACPA and IgM RF. Surprisingly, protein G-mediated removal of IgG from the serum eliminated positivity for IgM ACPA, suggesting that IgG ACPA-IgM RF complex was being detected. This assumption was confirmed by the detection of IgM RF in the eluate of protein G beads and citrullinated peptide-conjugated beads.CONCLUSIONS:In an attempt to detect IgM ACPA, we mostly revealed false positive reactions due to the presence of IgM molecules, which were not specific for citrullinated proteins, and IgG ACPA-IgM RF immune complex. The latter complex had been proposed to play a role in the pathogenesis of RA, and here, for the first time, we have demonstrated its presence in the sera of RA patients. |
PMID | 29465353 |