Medina C A, Teale J M
Department of Microbiology, University of Texas Health Science Center, San Antonio 78284-7758.
J Exp Med. 1993 May 1;177(5):1317-30. doi: 10.1084/jem.177.5.1317.
To determine the extent of kappa chain diversity in the preimmune repertoire early in development, kappa cDNA libraries were analyzed from 15-d old fetal omentum, 18-d-old fetal liver, and 3-wk old bone marrow. An anchored polymerase chain reaction approach was used to avoid bias for particular V kappa families. From the sequence analysis of 27 bone marrow clones, 10 different families and 20 unique V kappa genes were identified. In contrast, the V kappa expression in the fetus is highly restricted and clearly differs from the broader distribution see in 3-wk-old bone marrow. Although several V kappa families were represented in the fetal library including V kappa 9, V kappa 10, V kappa 4,5, V kappa 8, and V kappa 1, one or two members of individual families were observed repeatedly. The fetal liver and omentum libraries were found to be largely overlapping. Given the V kappa families/exons identified in the fetal sequences, the mechanism of kappa rearrangements in the early repertoire appears to occur predominantly by inversion. Importantly, the fetal repertoire was further restricted by dominant V kappa-J kappa combinations such as V kappa 4,5-J kappa 5, V kappa 9-J kappa 4, and V kappa 10-J kappa 1. Since in some cases independent rearrangements could be established, the results indicate a bias for particular V kappa-J kappa joins. The results also suggest that clonal expansion/selection in the fetal repertoire takes place after light chain rearrangement as opposed to at the pre-B cell level in the bone marrow. The restriction observed in kappa light chain expression together with known restrictions in gene usage and junctional diversity at the heavy chain level indicate a remarkably conserved fetal repertoire.
为了确定发育早期免疫前库中κ链多样性的程度，对来自15日龄胎儿大网膜、18日龄胎儿肝脏和3周龄骨髓的κ cDNA文库进行了分析。采用锚定聚合酶链反应方法以避免对特定Vκ家族产生偏差。通过对27个骨髓克隆的序列分析，鉴定出10个不同家族和20个独特的Vκ基因。相比之下，胎儿中的Vκ表达受到高度限制，明显不同于3周龄骨髓中更广泛的分布。尽管胎儿文库中存在几个Vκ家族，包括Vκ9、Vκ10、Vκ4,5、Vκ8和Vκ1，但个别家族的一两个成员被反复观察到。发现胎儿肝脏和大网膜文库在很大程度上重叠。根据胎儿序列中鉴定出的Vκ家族/外显子，早期库中κ重排的机制似乎主要通过倒位发生。重要的是，胎儿库进一步受到优势Vκ-Jκ组合的限制，如Vκ4,5-Jκ5、Vκ9-Jκ4和Vκ10-Jκ1。由于在某些情况下可以建立独立的重排，结果表明对特定Vκ-Jκ连接存在偏差。结果还表明，胎儿库中的克隆扩增/选择发生在轻链重排之后，而不是在骨髓中的前B细胞水平。在κ轻链表达中观察到的限制以及在重链水平上已知的基因使用和连接多样性限制表明胎儿库具有显著的保守性。
