Section for Medical Inflammation Research and 2 Section for Molecular Structural Biology, Department of Medical Biochemistry and Biophysics, Karolinska Institutet, 171 77 Stockholm, Sweden.
J Exp Med. 2014 Mar 10;211(3):405-11. doi: 10.1084/jem.20130968. Epub 2014 Feb 17.
Autoantibody formation is essential for the development of certain autoimmune diseases like rheumatoid arthritis (RA). Anti-type II collagen (CII) antibodies are found in RA patients; they interact with cartilage in vivo and are often highly pathogenic in the mouse. Autoreactivity to CII is directed to multiple epitopes and conserved between mice and humans. We have previously mapped the antibody response to CII in a heterogeneous stock cohort of mice, with a strong association with the IgH locus. We positioned the genetic polymorphisms and determined the structural requirements controlling antibody recognition of one of the major CII epitopes. Polymorphisms at positions S31R and W33T of the associated variable heavy chain (VH) allele were identified and confirmed by gene sequencing. The Fab fragment binding the J1 epitope was crystallized, and site-directed mutagenesis confirmed the importance of those two variants for antigen recognition. Back mutation to germline sequence provided evidence for a preexisting recognition of the J1 epitope. These data demonstrate a genetic association of epitope-specific antibody responses with specific VH alleles, and it highlights the importance of germline-encoded antibodies in the pathogenesis of antibody-mediated autoimmune diseases.
自身抗体的形成对于某些自身免疫性疾病的发展是必不可少的，如类风湿关节炎（RA）。RA 患者体内存在抗 II 型胶原（CII）抗体，它们与软骨体内相互作用，并且在小鼠中通常具有高度致病性。针对 CII 的自身反应性针对多个表位，并且在小鼠和人类之间保守。我们之前在一个异质 stock 队列的小鼠中对 CII 的抗体反应进行了定位，与 IgH 基因座有很强的关联。我们定位了遗传多态性，并确定了控制主要 CII 表位之一的抗体识别的结构要求。在相关的可变重链（VH）等位基因的位置 S31R 和 W33T 处发现了多态性，并通过基因测序进行了确认。结合 J1 表位的 Fab 片段被结晶，定点突变证实了这两个变体对抗原识别的重要性。返回到原始序列提供了对 J1 表位预先存在识别的证据。这些数据表明，表位特异性抗体反应与特定的 VH 等位基因存在遗传关联，并且突出了种系编码抗体在抗体介导的自身免疫性疾病发病机制中的重要性。
