Bonagura V R, Artandi S E, Davidson A, Randen I, Agostino N, Thompson K, Natvig J B, Morrison S L
Department of Pediatrics, Schneider Children's Hospital of Long Island Jewish Medical Center, New Hyde Park, NY 11042.
J Immunol. 1993 Oct 1;151(7):3840-52.
We have used chimeric IgG antibodies and their genetically engineered variants prepared by a combination of site-directed mutagenesis and exon exchange to define the structure(s) on IgG recognized by monoclonal rheumatoid factor (RF) autoantibodies from rheumatoid arthritis (RA) patients. Nineteen RF produced by EBV-transformed cell lines from the synovium or blood of RA patients were analyzed. Their binding patterns differ significantly from those seen with RF obtained from patients with Waldenstrom's macroglobulinemia (WMac). Half of the RA-derived RF bound IgG1, 2, and 4, but not 3 (Ga specificity), the common pattern in WMac. However, heterogeneity in fine specificity within the Ga reactivity pattern was observed. Moreover, seven others bound all four IgG subclasses, a pattern observed for only one WMac-derived RF from a patient who also had RA. Three RF had subclass specificities unlike any observed with WMac-derived RF. Most RA-derived RF bound IgG at a discontinuous epitope comprised of residues from both the CH2 and CH3 H chain constant regions. However, unlike any WMac-derived RF, one RA-derived RF bound IgG in CH2, another in CH3, and a third at an undetermined site outside of the CH2-CH3 interface. Some RA-derived RF bound aglycosylated IgG4 less well than glycosylated IgG4, suggesting that the carbohydrate moiety was important in establishing their binding epitope in CH2. These studies demonstrate that the repertoire of RF expressed by RA patients contains some unique binding specificities for IgG epitopes not found among our panel of WMac-derived RF. Our results therefore call into question whether WMac-derived RF with their limited diversity are appropriate models for disease-related RF. In addition, RF with their multiple specificities can serve as probes of antibody structure.
我们使用了嵌合IgG抗体及其通过定点诱变和外显子交换相结合制备的基因工程变体，以确定类风湿性关节炎（RA）患者的单克隆类风湿因子（RF）自身抗体所识别的IgG上的结构。分析了由RA患者滑膜或血液中EBV转化细胞系产生的19种RF。它们的结合模式与来自华氏巨球蛋白血症（WMac）患者的RF有显著差异。一半的RA来源的RF结合IgG1、2和4，但不结合3（Ga特异性），这是WMac中的常见模式。然而，在Ga反应模式内观察到精细特异性的异质性。此外，另外七种结合所有四种IgG亚类，这种模式仅在一名同时患有RA的WMac来源的RF中观察到。三种RF具有与WMac来源的RF不同的亚类特异性。大多数RA来源的RF在由CH2和CH3重链恒定区的残基组成的不连续表位处结合IgG。然而，与任何WMac来源的RF不同，一种RA来源的RF在CH2中结合IgG，另一种在CH3中结合，第三种在CH2-CH3界面之外的未确定位点结合。一些RA来源的RF与去糖基化的IgG4结合不如与糖基化的IgG4结合好，这表明碳水化合物部分对于在CH2中建立它们的结合表位很重要。这些研究表明，RA患者表达的RF库对于我们的WMac来源的RF组中未发现的IgG表位具有一些独特的结合特异性。因此，我们的结果质疑具有有限多样性的WMac来源的RF是否是与疾病相关的RF的合适模型。此外，具有多种特异性的RF可以作为抗体结构的探针。
