PDF(Pubmed)
Abstract：
Classification of patients with chronic lymphocytic leukemia (CLL) based on the somatic hypermutation (SHM) status of the clonotypic immunoglobulin heavy variable (IGHV) gene has established predictive and prognostic relevance. The SHM status is assessed based on the number of mutations within the IG heavy variable domain sequence, albeit only over the rearranged IGHV gene excluding the variable heavy complementarity determining region 3 (VH CDR3). This may lead to an underestimation of the actual impact of SHM, in fact overlooking the most critical region for antigen-antibody interactions, i.e. the VH CDR3. Here we investigated whether SHM may be present within the VH CDR3 of cases bearing \'truly unmutated\' IGHV genes (i.e. 100% germline identity across VH FR1-VH FR3) employing Next Generation Sequencing. We studied 16 patients bearing a \'truly unmutated\' CLL clone assigned to stereotyped subsets #1 (n=12) and #6 (n=4). We report the existence of SHM within the germline-encoded 3\'IGHV, IGHD, 5\'IGHJ regions of the VH CDR3 in both the main IGHV-IGHD-IGHJ gene clonotype and its variants. Recurrent somatic mutations were identified between different patients of the same subset, supporting the notion that they represent true mutational events rather than technical artefacts; moreover, they were located adjacent to/within AID hotspots, pointing to SHM as the underlying mechanism. In conclusion, we provide immunogenetic evidence for intra-VH CDR3 variations, attributed to SHM, in CLL patients carrying \'truly unmutated\' IGHV genes. Although the clinical implications of this observation remain to be defined, our findings offer a new perspective into the immunobiology of CLL, alluding to the operation of VH CDR3-restricted SHM in U-CLL.
摘要：
根据克隆型免疫球蛋白重变量（IGHV）基因的体细胞超突变（SHM）状态对慢性淋巴细胞白血病（CLL）患者进行分类已建立了预测和预后相关性。SHM状态基于IG重链可变结构域序列内的突变数量进行评估。尽管仅在重排的IGHV基因上，不包括可变重链互补决定区3（VHCDR3）。这可能导致低估了SHM的实际影响，事实上，忽略了抗原-抗体相互作用的最关键区域，即VHCDR3。在这里，我们调查了SHM是否可能存在于携带“真正未突变的IGHV基因（即跨VHFR1-VHFR3的100％种系同一性）的病例的VHCDR3中，采用下一代测序。我们研究了16例患者，这些患者具有“真正未突变的”CLL克隆，这些克隆被分配给定型的子集＃1（n=12）和＃6（n=4）。我们报告了在种系编码的3'IGHV中存在SHM，IGHD,主要IGHV-IGHD-IGHJ基因克隆型及其变体中VHCDR3的5个IGHJ区。在同一子集的不同患者之间发现了复发性体细胞突变，支持它们代表真正的突变事件而不是技术文物的概念；此外，它们位于AID热点附近/内部，指向SHM作为潜在机制。总之,我们提供了VH内CDR3变异的免疫遗传学证据，归因于SHM，在携带真正未突变的IGHV基因的CLL患者中。尽管这一观察的临床意义仍有待定义，我们的发现为CLL的免疫生物学提供了新的视角，暗示VHCDR3限制性SHM在U-CLL中的操作。
