Immunoglobulins emerging from B lymphocytes and capable of recognizing almost all kinds of antigens owing to the extreme diversity of their antigen‐binding portions, known as variable (V) regions, play an important role in immune responses. The exons encoding the V regions are known as V (variable), D (diversity), or J (joining) genes. V, D, J segments exist as multiple copy arrays on the chromosome. The recombination of the V(D)J gene is the key mechanism to produce antibody diversity. The recombinational process, including randomly choosing a pair of V, D, J segments, introducing double‐strand breaks adjacent to each segment, deleting (or inverting in some cases) the intervening DNA and ligating the segments together, is defined as V(D)J recombination, which contributes to surprising immunoglobulin diversity in vertebrate immune systems. To enhance both the ability of immunoglobulins to recognize and bind to foreign antigens and the effector capacities of the expressed antibodies, naive B cells will undergo class switching recombination (CSR) and somatic hypermutation (SHM). However, the genetics mechanisms of V(D)J recombination, CSR and SHM are not clear. In this review, we summarize the major progress in mechanism studies of immunoglobulin V(D)J gene recombination and CSR as well as SHM, and their regulatory mechanisms.

中文翻译：

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V（D）J重组，体细胞超突变和免疫球蛋白的类别转换重组：机制和调控。

B淋巴细胞产生的免疫球蛋白由于其抗原结合部分（称为可变（V）区）的极端多样性而能够识别几乎所有类型的抗原，在免疫反应中起重要作用。编码V区的外显子称为V（可变），D（多样性）或J（连接）基因。V，D，J段在染色体上以多个副本阵列的形式存在。V（D）J基因的重组是产生抗体多样性的关键机制。重组过程包括随机选择一对V，D，J片段，在每个片段附近引入双链断裂，删除（或在某些情况下将其反转）插入的DNA并将这些片段连接在一起，定义为V（D J重组，有助于脊椎动物免疫系统中令人惊讶的免疫球蛋白多样性。为了增强免疫球蛋白识别和结合外源抗原的能力以及表达的抗体的效应子能力，幼稚B细胞将经历类别转换重组（CSR）和体细胞超突变（SHM）。但是，V（D）J重组，CSR和SHM的遗传机制尚不清楚。在这篇综述中，我们总结了免疫球蛋白V（D）J基因重组和CSR以及SHM的机制研究的主要进展及其调控机制。