Home W A, Ford J E, Gibson D M
Département de Biochimie, Université de Sherbrooke, Quebec, Canada.
J Immunol. 1992 Dec 15;149(12):3927-36.
Analysis of 10 cDNA encoding lambda L chains of horse Ig indicated that this species may employ a relatively small number of variable region (V lambda) genes in the splenic B cell population. The V lambda sequences of all of the cDNA analyzed were closely related (> 88% identity at the nucleotide level) and were characterized by a deletion of the amino acid residue at position 3 compared with V lambda sequences so far described in other species. The 10 V lambda sequences could be grouped into three groups, V lambda 1 to V lambda 3, on the basis of a number of linked substitutions. Sequences within the groups showed the greatest divergence in the third cdr regions and at the V-J junctions. The junctional variation included amino acid substitutions on both sides of the V-J junction as well as the insertion or deletion of two to four amino acid residues. Four C lambda genes were identified in genomic blots of horse DNA, and three of these were found expressed in splenic cDNA. The fourth C lambda gene may represent a pseudogene, inasmuch as the associated J region possessed a defective heptamer joining sequence. Six of the nine possible V lambda-C lambda combinations were found in the cDNA analyzed, suggesting that genes belonging to groups V lambda 1 through V lambda 3 may rearrange to any one of three J lambda-C lambda genes. One V lambda germline gene was characterized and found to represent a distinct V lambda group (V lambda 4), not represented in the cDNA sequences analyzed. The number of germline V lambda genes was estimated to be 20 to 30, based on analysis of restriction fragments hybridizing with V lambda probes. On the basis of these data, we propose that the V lambda repertoire in horse may consist of relatively limited number of genes, of which only a few may be used at high frequency in the splenic B cell population. The results indicate that predominance of lambda-chains in horse Ig may not simply be due to the presence of a large germline V lambda gene repertoire.
对10个编码马Igλ轻链的cDNA进行分析表明，该物种在脾B细胞群体中可能使用相对较少数量的可变区（Vλ）基因。所有分析的cDNA的Vλ序列密切相关（核苷酸水平上同一性>88%），其特征是与迄今在其他物种中描述的Vλ序列相比，第3位氨基酸残基缺失。根据一些连锁替换，10个Vλ序列可分为三组，即Vλ1至Vλ3。组内序列在第三个互补决定区（cdr）和V-J连接区差异最大。连接区变异包括V-J连接两侧的氨基酸替换以及两到四个氨基酸残基的插入或缺失。在马DNA的基因组印迹中鉴定出4个Cλ基因，其中3个在脾cDNA中表达。第四个Cλ基因可能代表一个假基因，因为相关的J区具有缺陷的七聚体连接序列。在所分析的cDNA中发现了9种可能的Vλ-Cλ组合中的6种，这表明属于Vλ1至Vλ3组的基因可能重排至3个Jλ-Cλ基因中的任何一个。对一个Vλ种系基因进行了表征，发现它代表一个独特的Vλ组（Vλ4），在所分析的cDNA序列中未出现。根据与Vλ探针杂交的限制性片段分析，估计种系Vλ基因的数量为20至30个。基于这些数据，我们提出马的Vλ库可能由相对有限数量的基因组成，其中只有少数基因可能在脾B细胞群体中高频使用。结果表明，马Ig中λ链的优势可能不仅仅是由于存在大量的种系Vλ基因库。
