Deane M, Mackenzie L E, Stevenson F K, Youinou P Y, Lydyard P M, Mageed R A
Department of Hematology, Royal Free Hospital, London, UK.
Scand J Immunol. 1993 Oct;38(4):348-58. doi: 10.1111/j.1365-3083.1993.tb01737.x.
In a recent study we have observed a high frequency expression of cross-reactive idiotypes encoded by genes from the relatively small VH4 family of immunoglobulin heavy chain genes in cord blood B-lymphocyte lines. Furthermore, we have demonstrated a selective pattern of expression of two VH4-associated cross-reactive idiotype (CRI) in B-lymphocyte lines established from CD5+ and CD5- cord blood B-lymphocytes. There was a restricted expression of one CRI marker recognized by the 9G4 monoclonal antibody in lines established from CD5+ B-lymphocytes but not in those established from the CD5- population. In the current study we examine the molecular basis for the selective pattern of CRI expression. Nucleotide-sequence analysis of functional immunoglobulin heavy chain (IgH) gene rearrangements in three CD5+ lines expressing the CRI recognised by 9G4 reveal that all use a single gene from the VH4 family, the V4.21 gene. However, all three lines have distinct third complementarity determining regions (CDR3) implying different clonal origins. In contrast, four cord blood cell lines (two established from CD5+ B-lymphocytes) expressing the CRI recognized by MoAb Lc1 have functional IgH gene rearrangements involving two different genes from the VH4 family, the V71-4, and V2-1 genes. Antigen specificity analysis reveals that all three 9G4-reactive lines produce antibodies that react with the I and/or i red blood cell carbohydrate antigens. These data suggest that the distinction in VH4 gene use in CD5+ B-lymphocytes in cord blood results from a selection process in vivo that shapes the repertoire of CD5+ B-lymphocytes. This study extends recent observations that the monoclonal anti-CRI antibodies 9G4 and Lc1 are markers of two distinct subgroups of proteins encoded by two subsets of genes within the VH4 family. Furthermore, it appears that amino acid residues in framework region one and complementarity determining region two are critical for the expression of the cross reactive idiotypes and the serological distinction between the two subgroups of proteins.
在最近的一项研究中，我们观察到在脐血B淋巴细胞系中，由免疫球蛋白重链基因相对较小的VH4家族的基因编码的交叉反应独特型有高频表达。此外，我们已经证明在从CD5 +和CD5 -脐血B淋巴细胞建立的B淋巴细胞系中，两种VH4相关交叉反应独特型（CRI）有选择性的表达模式。在从CD5 + B淋巴细胞建立的细胞系中，有一种由9G4单克隆抗体识别的CRI标志物表达受限，而在从CD5 -群体建立的细胞系中则没有。在当前的研究中，我们研究了CRI表达选择性模式的分子基础。对三个表达由9G4识别的CRI的CD5 +细胞系中功能性免疫球蛋白重链（IgH）基因重排的核苷酸序列分析表明，所有细胞系都使用来自VH4家族的单个基因，即V4.21基因。然而，所有这三个细胞系都有不同的第三互补决定区（CDR3），这意味着它们有不同的克隆起源。相比之下，四个表达由单克隆抗体Lc1识别的CRI的脐血细胞系（两个从CD5 + B淋巴细胞建立）的功能性IgH基因重排涉及来自VH4家族的两个不同基因，即V71 - 4和V2 - 1基因。抗原特异性分析表明，所有三个与9G4反应的细胞系产生的抗体都与I和/或i红细胞碳水化合物抗原发生反应。这些数据表明，脐血中CD5 + B淋巴细胞在VH4基因使用上的差异是由体内塑造CD5 + B淋巴细胞库的选择过程导致的。这项研究扩展了最近的观察结果，即单克隆抗CRI抗体9G4和Lc1是由VH4家族内两个基因子集编码的两个不同蛋白质亚组的标志物。此外，似乎框架区一和互补决定区二中的氨基酸残基对于交叉反应独特型的表达以及这两个蛋白质亚组之间的血清学差异至关重要。
