Identification of novel citrullinated antigens in rheumatoid arthritis (RA) and the role of anti-CCP antibody in the pathogenesis of RA

抗CCP(环瓜氨酸肽)抗体是类风湿关节炎(RA)早期诊断和关节破坏的有用的血清学标志物。然而，抗CCP抗体在RA发病机制中的作用尚不明确。因此，目前尚不清楚类风湿滑膜炎是否产生了抗CCP抗体，以及抗CCP抗体是否参与了类风湿关节炎的联合破坏。到目前为止，瓜氨酸化形式的纤维蛋白原、微丝蛋白、波形蛋白被认为是类风湿关节炎的自身抗原。然而，这些瓜氨酸化抗原在类风湿滑膜中的具体存在尚不清楚。在本研究中，我们建立了一种全新的检测抗瓜氨酸肽抗体的酶联免疫吸附试验体系，使用瓜氨酸化形式的类风湿滑膜细胞裂解物、重组P53和合成的纤维蛋白原肽。虽然目前的ELISA系统的灵敏度低于市售的抗CCP2试剂盒，但仍有可能根据我们的抗瓜氨酸肽抗体的结果对RA患者进行分类。我们还鉴定了瓜氨酸多肽是类风湿关节炎患者滑液中的鱼精蛋白结合组分。我们进一步鉴定了瓜氨酸型纤维蛋白原在类风湿滑液中的特异性。进一步研究我们鉴定的瓜氨酸抗原的生化和免疫学性质及其免疫原性将有助于阐明类风湿关节炎的发病机制。

Anti-CCP (cyclic citrullinated peptides) antibody has been demonstrated to be a useful serological marker for early diagnosis as well as prediction of joint destruction of rheumatoid arthritis (RA). However, the role of anti-CCP antibody in the pathogenesis of RA has not been established. Thus it is not known whether anti-CCP is produced as a result of rheumatoid synovitis and whether cirtrullination of putative autoantigens by peptidylarginine deiminases (PADIs) and subsequent induction of anti-CCP antibody is involved for the joint destruction in RA. So far, citrullinated forms of fibrinogen, filaggrin, vimentin have been implicated as putative autoantigens in RA. However, the specific presence of such citrullinated antigens in rheumatoid synovium has remained to be elucidated.In this study we established a brand-new ELISA system to detect anti-citrullinated peptide antibody using citrullinated form of rheumatoid synovial cell lysate, recombinant p53 and synthetic fibrinogen peptide. Although the sensitivity of the present ELISA system was inferior to the commercially available anti-CCP2 kit, it was possible to classify RA patients according to the results of our anti-citrullinated peptide antibodies. We also identified citrullinated peptides as a protamine-binding fraction of synovial fluids from RA patients. We further identified citrullinated form of fibrinogen specifically in rheumatoid synovial fluids. Further studies examining biochemical and immunological nature of the citrullinated antigens that we have identified and their immunogenicity would be warranted for elucidation of the pathogenesis of RA.