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）抗体已被证明是一种有用的血清学标志物，可用于类风湿关节炎（RA）的早期诊断和关节破坏预测。然而，抗ccp抗体在RA发病机制中的作用尚未确定。因此，尚不清楚类风湿滑膜炎是否产生抗ccp，也不清楚肽精氨酸脱亚胺酶（PADIs）对假定的自身抗原进行循环化并随后诱导抗ccp抗体是否与类风湿关节炎的关节破坏有关。到目前为止，瓜氨酸化形式的纤维蛋白原，聚丝蛋白，波形蛋白被认为是类风湿性关节炎的自身抗原。然而，这种瓜氨酸化抗原在类风湿滑膜中的特异性存在仍有待阐明。本研究利用类风湿滑膜细胞裂解液瓜氨酸化形式、重组p53和合成纤维蛋白原肽，建立了一套全新的ELISA检测抗瓜氨酸化肽抗体系统。虽然本ELISA系统的敏感性不如市售的抗ccp2试剂盒，但可以根据抗瓜氨酸肽抗体的结果对RA患者进行分类。我们还发现瓜氨酸化肽是类风湿性关节炎患者滑液中蛋白结合部分。我们进一步鉴定了类风湿性滑液中纤维蛋白原的瓜氨酸化形式。进一步研究我们所鉴定的瓜氨酸化抗原的生化和免疫学性质及其免疫原性将为阐明RA的发病机制提供保证。

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.