Roux K H, Greenspan N S
Department of Biological Science, Florida State University, Tallahassee 32306-3050.
Mol Immunol. 1994 Jun;31(8):599-606. doi: 10.1016/0161-5890(94)90167-8.
We have previously used immunoelectron microscopy (IEM) to generate a three-dimensional map of idiotypic (Id) and isotypic epitopes on the Fab arms of HGAC 39 (Roux et al., 1987, Proc. natn. Acad. Sci. U.S.A. 84, 4984-4988), a mouse IgG3 monoclonal antibody (Mab). In this report, we analyse the geometry of the various types of immune complexes formed by the interaction of HGAC 39 with Mab directed against four mapped epitopes. Moreover, by sampling of reaction mixtures over time, we show that the kinetics of each of the subpopulations of immune complexes, as defined by geometric configuration, can be determined. The data show that for each antibody (Ab)-HGAC 39 combination the rate of immune complex formation was greatest during the first 1.5-3.5 min but that additional complexes formed through the remainder of the half hour assay period. As anticipated, complexes composed of even number units predominated (primarily dimers and tetramers) and most of these were in the form of closed rings. The data also suggest that the location and orientation of the epitopes on HGAC 39 to which the monoclonal antibodies were bound has an influence on the types of immune complexes generated. Specifically we observed that those anti-idiotype Abs that bind to the distal tip of Fab arms (i.e. in the CDR) are less likely to produce bivalently associated ringed dimers than antibodies that bind to epitopes that are proximal to the CDR and that project laterally from the surface of the Fab arms. These data are interpreted in terms of restrictions on hinge mediated flexibility and steric inhibition between adjacent Fab arms on HGAC 39.
我们之前曾使用免疫电子显微镜（IEM）生成了HGAC 39（一种小鼠IgG3单克隆抗体（Mab））Fab臂上独特型（Id）和同种型表位的三维图谱（Roux等人，1987年，《美国国家科学院院刊》84，4984 - 4988）。在本报告中，我们分析了HGAC 39与针对四个已定位表位的单克隆抗体相互作用形成的各种类型免疫复合物的几何结构。此外，通过对反应混合物随时间进行取样，我们表明可以确定由几何构型定义的每个免疫复合物亚群的动力学。数据显示，对于每种抗体（Ab） - HGAC 39组合，免疫复合物形成速率在最初的1.5 - 3.5分钟内最快，但在半小时的检测期剩余时间内仍会形成额外的复合物。正如预期的那样，由偶数个单位组成的复合物占主导（主要是二聚体和四聚体），并且其中大多数呈闭环形式。数据还表明，单克隆抗体所结合的HGAC 39上表位的位置和方向对所产生的免疫复合物类型有影响。具体而言，我们观察到那些结合到Fab臂远端（即在互补决定区（CDR））的抗独特型抗体比结合到CDR近端且从Fab臂表面侧向突出的表位的抗体产生双价结合环状二聚体的可能性更小。这些数据根据对HGAC 39上相邻Fab臂之间铰链介导的灵活性和空间位阻的限制来解释。
