Jacobi A M, Hansen A, Burmester G R, Dörner T, Lipsky P E
Dept. Med. Charite University Hospitals Berlin, Germany.
Autoimmunity. 2000;33(1):61-76. doi: 10.3109/08916930108994110.
To determine the impact of somatic hypermutation and selective influences on the V(H) gene repertoire in SLE, the mutational frequency and pattern of mutations in nonproductively and productively rearranged V(H) genes obtained from genomic DNA of individual CD19+ B cells were analyzed in a patient with SLE. The mutational frequencies of nonproductive (6.54 x 10(-2)) as well as of productive (4.38 x 10(-2)) V(H) rearrangements were significantly higher in the SLE patient than in normal controls (3.8 x 10(-2), p<0.001 and 3.3 x 10(-2); p<0.001, respectively). Analysis of nonproductive rearrangements documented only minor abnormalities of the targeting of the mutator in the SLE patient. The majority of "mutational hot spots", although different than in normals, appeared in the CDRs and an increased frequency of mutations in RGYW/WRCY sequences was observed. Moreover, no biases in base pair changes were found in the nonproductive repertoire. In contrast, there was a selection against A and T mutations and towards G mutations within the productive repertoire. Importantly, there were no significant differences in the R/S ratios of mutations within the FRs between the nonproductive and productive repertoire consistent with abnormalities in elimination of B cells expressing V(H) genes with these mutations. The result of this abnormality was a significantly higher R/S ratio of the V(H)genes in the productive repertoire of the SLE patient compared to normals (p<0.05). These data indicate that the mutational machinery was markedly enhanced in this SLE patient but exhibited nearly normal targeting, whereas selective influences were abnormal. These findings suggest that both enhanced mutational activity and disturbances in selection may have played a role in the emergence of autoreactivity in this SLE patient.
为了确定体细胞超突变和选择性影响对系统性红斑狼疮（SLE）中V(H)基因库的作用，我们分析了一名SLE患者单个CD19⁺ B细胞基因组DNA中未产生功能性重排和产生功能性重排的V(H)基因的突变频率及突变模式。该SLE患者未产生功能性重排（6.54×10⁻²）以及产生功能性重排（4.38×10⁻²）的V(H)重排的突变频率显著高于正常对照（分别为3.8×10⁻²，p<0.001和3.3×10⁻²；p<0.001）。对未产生功能性重排的分析表明，该SLE患者中突变引入机制仅有轻微异常。虽然与正常人不同，但大多数“突变热点”出现在互补决定区（CDR），并且观察到RGYW/WRCY序列中的突变频率增加。此外，在未产生功能性重排的基因库中未发现碱基对变化的偏差。相比之下，在产生功能性重排的基因库中存在对A和T突变的选择倾向以及对G突变的选择。重要的是，未产生功能性重排和产生功能性重排的基因库中框架区（FR）内突变的R/S比值没有显著差异，这与消除表达带有这些突变的V(H)基因的B细胞异常一致。这种异常的结果是，与正常人相比，该SLE患者产生功能性重排的基因库中V(H)基因的R/S比值显著更高（p<0.05）。这些数据表明，该SLE患者的突变机制明显增强，但靶向作用几乎正常，而选择性影响是异常的。这些发现提示，增强的突变活性和选择紊乱可能在该SLE患者自身反应性的出现中都发挥了作用。
