Beishuizen A, Verhoeven M A, Mol E J, van Dongen J J
Department of Immunology, University Hospital Dijkzigt/Erasmus University, Rotterdam, The Netherlands.
Leukemia. 1994 Dec;8(12):2228-36; discussion 2237-9.
Immunoglobulin light-chain (IgL) gene rearrangements occur in a sequential order during normal B-cell differentiation with Ig kappa gene rearrangements prior to Ig lambda gene rearrangements. Therefore, Ig kappa producing B-cells usually retain Ig lambda genes in germline configuration, whereas the Ig kappa genes are generally deleted on one or both alleles in most Ig lambda producing B-cells. The deletion processes in the Ig kappa locus are mediated via rearrangement of the kappa deleting element (Kde), which is located approximately 24 kb downstream of the constant (C) kappa gene segment. Kde rearrangements can delete the C kappa region (including the Ig kappa enhancer) or the complete joining (J) kappa-C kappa region via rearrangements to a heptamer recombination signal sequence in the J kappa-C kappa intron (intron RSS), or via rearrangement to a variable (V) kappa gene segment, respectively. To improve the Southern blot detection of clonal Ig kappa gene rearrangements and deletions in B-lineage malignancies, we developed a new set of optimal J kappa, C kappa, and Kde probes, and made a detailed restriction map of the J kappa, C kappa, and Kde region. Extensive Southern blot studies revealed that rearrangements in the J kappa gene region are optimally detectable by use of a J kappa probe in combination with at least two appropriate restriction enzymes, i.e. BamHI, BglII, EcoRI, HindIII, and/or SacI. J kappa gene rearrangements are also detectable with the C kappa probe in BglII and BamHI digests, if no deletion of the C kappa region has occurred. The two different types of Kde-mediated J kappa and/or C kappa gene deletions are easily detectable with the Kde probe in BglII, HindIII and/or EcoRI digests. This is in contrast to the inaccurate information obtained with the J kappa and C kappa probes, because these probes can detect deletions only in the form of decreased densities of J kappa and/or C kappa germline bands in the absence of rearranged bands. Our detailed analysis of 217 B-lineage leukemias revealed that 62% (69/111) of precursor B-cell acute lymphoblastic leukemias had rearranged and/or deleted Ig kappa genes. All 53 Ig lambda+ chronic B-cell leukemias contained Ig kappa gene deletions; in 75% this concerned biallelic J kappa and/or C kappa gene deletions. Virtually all Ig kappa gene deletions appeared to be mediated via Kde rearrangements, while only 1.5% of the Ig kappa gene deletions were mediated via an alternative deletion mechanism which involved the J kappa region.
免疫球蛋白轻链（IgL）基因重排在正常B细胞分化过程中按顺序发生，Igκ基因重排在Igλ基因重排之前。因此，产生Igκ的B细胞通常将Igλ基因保留在种系构型中，而在大多数产生Igλ的B细胞中，Igκ基因通常在一个或两个等位基因上被删除。Igκ基因座的缺失过程是通过κ删除元件（Kde）的重排介导的，Kde位于恒定（C）κ基因片段下游约24 kb处。Kde重排可通过重排至Jκ-Cκ内含子（内含子RSS）中的七聚体重组信号序列，或分别重排至可变（V）κ基因片段，从而删除Cκ区域（包括Igκ增强子）或完整的连接（J）κ-Cκ区域。为了改进Southern印迹法检测B系恶性肿瘤中克隆性Igκ基因重排和缺失，我们开发了一组新的最佳Jκ、Cκ和Kde探针，并制作了Jκ、Cκ和Kde区域的详细限制性图谱。广泛的Southern印迹研究表明，通过使用Jκ探针与至少两种合适的限制性内切酶（即BamHI、BglII、EcoRI、HindIII和/或SacI）联合使用，可最佳地检测Jκ基因区域的重排。如果没有发生Cκ区域的缺失，在BglII和BamHI消化物中用Cκ探针也可检测到Jκ基因重排。在BglII、HindIII和/或EcoRI消化物中用Kde探针可轻松检测到两种不同类型的Kde介导的Jκ和/或Cκ基因缺失。这与用Jκ和Cκ探针获得的不准确信息形成对比，因为这些探针只能在没有重排条带的情况下，以Jκ和/或Cκ种系条带密度降低的形式检测缺失。我们对217例B系白血病的详细分析表明，62%（69/111）的前体B细胞急性淋巴细胞白血病存在重排和/或缺失的Igκ基因。所有53例Igλ+慢性B细胞白血病均含有Igκ基因缺失；其中75%涉及双等位基因Jκ和/或Cκ基因缺失。几乎所有的Igκ基因缺失似乎都是通过Kde重排介导的，而只有1.5%的Igκ基因缺失是通过涉及Jκ区域的另一种缺失机制介导的。
