Department of Immunology, Center of Immunomolecular Engineering, Innovation and Practice Base for Graduate Students Education, Zunyi Medical University, Zunyi, China.
Cell Mol Life Sci. 2023 Oct 7;80(11):319. doi: 10.1007/s00018-023-04973-8.
Since the initial report of V (D) J "allelic exclusion/inclusion" (allelic exclusion rearrangement or allelic inclusion rearrangement) and the concept of the "dual B cell receptor (BCR)" in 1961, despite ongoing discoveries, the precise proportion and source mechanism of dual BCR under physiological conditions have been puzzling immuologists. This study takes advantage of the single cell B cell receptor sequencing (scBCR-seq) technology, which can perfectly match the heavy and light chains of BCR at the level of a single B cell, and obtain the full length mRNA sequence of the complementary determining region 3 (CDR3). Through analyzing the pairing of functional IGH (immunoglobulin heavy chain) and IGL (immunoglobulin light chain) in single B cell from both human and mouse bone marrow and peripheral blood, it was observed that dual BCR B cells exhibit stable and high levels of expression. Among them, the human bone marrow and peripheral blood contain about 10% dual (or multiple) BCR B cells, while in mouse peripheral blood and bone marrow memory B cells, this proportion reaches around 20%. At the same time, we innovatively found that in each research sample of humans and mice, there are three (or more) functional rearrangements (mRNA level) of a single chain in a single B cell. By analyzing the position, direction and other compositional characteristics of the V(D)J gene family, we found that at least two (or more) of them are derived from over two (or more) specific allelic inclusion rearrangements of a single chromosome (mRNA molecular level evidence), our findings also highlighted the necessity of classified single cell sequencing data based on single, dual (or multiple) and cannot be assembled into BCR when analyzing the B cell repertoire. The results of this article provides new methods and modeling references for evaluating the proportion and source mechanisms of dual BCR B cells, as well as potential significance of allelic inclusion (exclusion escape) of V(D)J rearrangement.
自 1961 年首次报道 V(D)J“等位基因排斥/包含”（等位基因排斥重排或等位基因包含重排）和“双 B 细胞受体（BCR）”概念以来，尽管不断有新发现，但在生理条件下双 BCR 的精确比例和来源机制一直令免疫学家感到困惑。本研究利用单细胞 B 细胞受体测序（scBCR-seq）技术，该技术可以在单个 B 细胞水平上完美匹配 BCR 的重链和轻链，并获得互补决定区 3（CDR3）的全长 mRNA 序列。通过分析来自人和小鼠骨髓和外周血的单个 B 细胞中功能性 IGH（免疫球蛋白重链）和 IGL（免疫球蛋白轻链）的配对，观察到双 BCR B 细胞表现出稳定且高水平的表达。其中，人骨髓和外周血中约含有 10%的双（或多）BCR B 细胞，而在小鼠外周血和骨髓记忆 B 细胞中，这一比例达到约 20%。同时，我们创新性地发现，在人和小鼠的每个研究样本中，单个 B 细胞中存在三种（或更多）单个链的功能性重排（mRNA 水平）。通过分析 V(D)J 基因家族的位置、方向和其他组成特征，我们发现至少有两个（或更多）来自于单个染色体的两个（或更多）特定的等位基因包含重排（mRNA 分子水平证据），我们的研究结果还强调了在分析 B 细胞库时，基于单个、双（或多）以及不能组装成 BCR 的分类对单细胞测序数据进行分析的必要性。本文的研究结果为评估双 BCR B 细胞的比例和来源机制以及 V(D)J 重排的等位基因包含（排除逃逸）的潜在意义提供了新的方法和建模参考。
