Guo J, Mcintosh R S, Czarnocka B, Weetman A P, Rapoport B, McLachlan S M
Thyroid Molecular Biology Unit, Veterans' Administration Medical Center and University of California, San Francisco 94121, USA.
Clin Exp Immunol. 1998 Feb;111(2):408-14. doi: 10.1046/j.1365-2249.1998.00492.x.
An immunodominant region recognized by serum autoantibodies has been defined on the autoantigen thyroid peroxidase (TPO) using recombinant human TPO-specific Fab or a panel of mouse MoAbs. We have now analysed the epitopic relationships between the four recombinant Fab that identify the A and B domains of the TPO immunodominant region and (i) the mouse TPO MoAb as well as (ii) nine new TPO-specific Fab isolated independently. Competition between mouse MoAbs and recombinant Fab for binding to 125I-TPO revealed three patterns. First, for MoAbs 15, 59, 64 and 18, TPO binding was virtually abolished (approximately 90%) by Fab which define the A domain of TPO, with less inhibition by B domain Fab. Second, for MoAbs 2, 9 and 47, the Fab competed much less for TPO binding, and, when detectable, inhibition was predominantly with B domain Fab (65-20%). Third, for MoAbs 53, 30, 1, 24 and 40, none of the Fab competed effectively for 125I-TPO binding. Thus, the epitopes for MoAbs 18, 59, 64 and 15 correspond to those of the A domain defined by the human Fab, and the epitopes for MoAbs 2, 9 and 47 correspond to those of the B domain. In the second part of the study, competition studies demonstrated that the epitopes of nine new Fab corresponded to those of the four Fab that define the immunodominant region. For four new Fab, TPO binding was inhibited to a greater extent by B- than by A-domain Fab (65-95% versus <50%). In contrast, for five new Fab the A-domain Fab were more effective inhibitors (approximately 90%) than the B-domain Fab. In addition, consistent with previous observations, all five new Fab with 02/012 kappa L chains, but none of the new Fab with non-O2/O121 chains, interacted with A-domain epitopes. In conclusion, we have established the epitopic relationships between recombinant human Fab and mouse MoAbs that define the TPO immunodominant region on TPO. Further, analysis of recombinant TPO Fab isolated from patients on three continents strengthens the paradigm of a relationship between autoantibody epitopic recognition and immunoglobulin gene usage.
利用重组人甲状腺过氧化物酶（TPO）特异性Fab或一组小鼠单克隆抗体（MoAbs），已在自身抗原甲状腺过氧化物酶（TPO）上确定了一个血清自身抗体识别的免疫显性区域。我们现在分析了识别TPO免疫显性区域A和B结构域的四种重组Fab与（i）小鼠TPO单克隆抗体以及（ii）九个独立分离的新的TPO特异性Fab之间的表位关系。小鼠单克隆抗体和重组Fab之间竞争与125I-TPO结合显示出三种模式。首先，对于单克隆抗体15、59、64和18，定义TPO A结构域的Fab几乎完全消除了（约90%）TPO结合，B结构域Fab的抑制作用较小。其次，对于单克隆抗体2、9和47，Fab对TPO结合的竞争要小得多，并且在可检测到的情况下，抑制主要是由B结构域Fab（65%-20%）引起的。第三，对于单克隆抗体53、30、1、24和40，没有一种Fab能有效地竞争125I-TPO结合。因此，单克隆抗体18、59、64和15的表位与人类Fab定义的A结构域的表位相对应，单克隆抗体2、9和47的表位与B结构域的表位相对应。在研究的第二部分，竞争研究表明九个新Fab的表位与定义免疫显性区域的四个Fab的表位相对应。对于四个新Fab，B结构域Fab比A结构域Fab对TPO结合的抑制作用更大（65%-95%对<50%）。相反，对于五个新Fab，A结构域Fab比B结构域Fab是更有效的抑制剂（约90%）。此外，与先前的观察结果一致，所有五个具有02/012 κ轻链的新Fab，但没有一个具有非O2/O121链的新Fab，与A结构域表位相互作用。总之，我们已经建立了定义TPO上TPO免疫显性区域的重组人Fab与小鼠单克隆抗体之间的表位关系。此外，对来自三大洲患者分离的重组TPO Fab的分析加强了自身抗体表位识别与免疫球蛋白基因使用之间关系的范例。
