Potter K N, Li Y, Pascual V, Williams R C, Byres L C, Spellerberg M, Stevenson F K, Capra J D
Department of Microbiology, University of Texas Southwestern Medical Center, Dallas 75235.
J Exp Med. 1993 Oct 1;178(4):1419-28. doi: 10.1084/jem.178.4.1419.
The anti-idiotypic (anti-Id) antibody (Ab) 9G4 binds a cross-reactive idiotope (CRI) present in a select group of human autoantibodies. This Id has been localized to the portion of immunoglobulin (Ig) heavy (H) chains encoded by the VH4-21 gene segment, a member of the human VH4 family. This gene segment is utilized by essentially all cold agglutinin (CA) Abs with I/i specificity isolated from patients with CA disease stemming from chronic lymphoproliferative disorders. In this study, mutational analysis of a CA has been used to determine the structural basis for 9G4 binding to Abs utilizing the VH4-21 gene segment. Recombinant CA H chain mutants were produced and their 9G4 reactivity determined. Mutants were generated by exchanging VH4-21 sequences in the FR1, CDR1, and CDR2 with corresponding sequences from a closely related gene segment V71-2, a VH4 family member that is associated neither with Abs having CA activity nor with Abs that react with 9G4. The results indicate that the motif AVY at amino acid positions 23-25 in FR1 defines the 9G4 idiotope. Reaction of these recombinant Abs with a polyclonal rabbit anti-CA antiserum absorbed to render it specific for a CA CRI also maps predominantly to FR1. These findings indicate that the solvent-exposed FR1 plays an important role in eliciting an immune response to Igs.
抗独特型（抗Id）抗体9G4可结合一组特定人类自身抗体中存在的交叉反应性独特型（CRI）。该独特型已定位至由VH4-21基因片段编码的免疫球蛋白（Ig）重链（H链）部分，VH4-21基因片段是人类VH4家族的成员。基本上所有从慢性淋巴细胞增殖性疾病引起的冷凝集素（CA）病患者中分离出的具有I/i特异性的CA抗体都利用了该基因片段。在本研究中，对一种CA进行了突变分析，以确定利用VH4-21基因片段的抗体与9G4结合的结构基础。制备了重组CA重链突变体并测定其与9G4的反应性。通过将FR1、CDR1和CDR2中的VH4-21序列与密切相关基因片段V71-2的相应序列进行交换来产生突变体，V71-2是VH4家族成员，既不与具有CA活性的抗体相关，也不与与9G4反应的抗体相关。结果表明，FR1中第23 - 25位氨基酸处的基序AVY定义了9G4独特型。这些重组抗体与经吸收以使其对CA CRI具有特异性的多克隆兔抗CA抗血清的反应也主要定位于FR1。这些发现表明，暴露于溶剂中的FR1在引发针对Ig的免疫反应中起重要作用。
