Araki R, Itoh M, Hamatani K, Abe M
Cell Biology Laboratory, Department of Radiobiology, Radiation Effects Research Foundation, 8-6 Nakagawa 1 chome, Nagasaki 850, Japan.
Int Immunol. 1996 Jul;8(7):1045-53. doi: 10.1093/intimm/8.7.1045.
SCID mice are profoundly immunodeficient, resulting from an inability to carry out the V(D)J recombination reaction during both B cell and T cell development. Recently, however, it was revealed that normal rearrangement frequently did occur in the TCR delta and gamma chain loci in the SCID thymus. To evaluate whether the normal rearrangement occurring in SCID is a T-cell-specific phenomenon, we directly cloned using PCR the DQ52-JH2 and DFL16.1-JH2 rearranged segments of the IgH gene from SCID bone marrow. The subsequent analysis revealed that normal V(D)J recombination occurred in a significant number of the analyzed clones. By quantitative Southern hybridization it was shown that the quantity of normal DQ52-JH2 joints existing in the SCID bone marrow is approximately 4-7% that in normal bone marrow. D-JH rearrangement in SCID mice and normal mice differs in the frequency of nucleotide insertion (N insertion). Although most of the normal mouse clones exhibited N insertion in the D-JH rearrangement, in SCID mouse clones N insertion was identified in only a few D-JH rearrangements. Furthermore, in several normal rearranged clones, the recombination occurred at the short homologous sequence. These observations suggest that the V(D)J recombination of IgH normally occurs at the early stage of SCID B cell development, just as TCR gene rearrangement occurs during SCID T cell development. Furthermore, the features of rearranged products isolated from SCID bone marrow cells were remarkably similar to those from leaky SCID mice.
严重联合免疫缺陷（SCID）小鼠存在严重的免疫缺陷，这是由于在B细胞和T细胞发育过程中无法进行V(D)J重组反应所致。然而，最近有研究表明，在SCID胸腺中，TCRδ和γ链基因座经常会发生正常的重排。为了评估SCID中发生的正常重排是否是T细胞特异性现象，我们利用聚合酶链反应（PCR）直接从SCID骨髓中克隆了IgH基因的DQ52-JH2和DFL16.1-JH2重排片段。随后的分析表明，在大量分析的克隆中发生了正常的V(D)J重组。通过定量Southern杂交显示，SCID骨髓中存在的正常DQ52-JH2接头数量约为正常骨髓中的4-7%。SCID小鼠和正常小鼠的D-JH重排在核苷酸插入（N插入）频率上有所不同。虽然大多数正常小鼠克隆在D-JH重排中表现出N插入，但在SCID小鼠克隆中，仅在少数D-JH重排中发现了N插入。此外，在几个正常重排的克隆中，重组发生在短同源序列处。这些观察结果表明，IgH的V(D)J重组通常发生在SCID B细胞发育的早期阶段，就像TCR基因重排在SCID T细胞发育过程中发生一样。此外，从SCID骨髓细胞中分离出的重排产物的特征与渗漏型SCID小鼠的重排产物特征非常相似。
