Molecular single-cell analysis reveals that CD5-positive peripheral blood B cells in healthy humans are characterized by rearranged V-kappa genes lacking somatic mutation
Molecular single-cell analysis reveals that CD5-positive peripheral blood B cells in healthy humans are characterized by rearranged V-kappa genes lacking somatic mutation
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DOI：
10.1172/jci119691
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发表时间：
1997-10-01
影响因子：
15.9
通讯作者：
Kuppers, R
中科院分区：
文献类型：
--
作者：
Fischer, M;Klein, U;Kuppers, R
表达CD5细胞表面抗原的B细胞参与了某些B细胞恶性肿瘤和自身免疫性疾病，从小鼠研究中发现，CD5(+) B细胞代表了一种独立的B淋巴细胞谱系，与传统的（CD5(-)） B细胞不同，CD5(+) B细胞不被驱动进入T细胞依赖性免疫反应，在这种免疫反应中，重排的可变(V)区基因通过体细胞超突变而多样化。在这种背景下，人类疾病相关的CD5阳性自身反应性B细胞以及B细胞慢性淋巴细胞白血病可以携带体细胞突变的V区基因，这是一个令人惊讶的发现。最近对健康成人CD5(+) B细胞的V基因分析并没有清晰地显示出所有CD5(+) B细胞中体细胞突变的比例。在这项工作中，我们使用分子单细胞分析来可靠地确定健康人体内CD5(+) B细胞突变的频率：通过流式细胞术分离出单个表达CD5（+）的kappa轻链外周血B细胞，并通过PCR扩增出重排的V kappa基因，分析了来自一个供者的CD5(+)CD19(+) B细胞，由于在来自另外两个供者的IgM(+)IgD（+）和IgM(+)IgD（-）细胞中发现了CD5(+) B细胞（但在类别转换细胞中几乎没有），因此分别研究了与这些表达IgM亚群对应的单个细胞。重排的V-kappa基因序列分析显示，健康人CD5(+) B细胞大部分（如果不是全部）携带未突变的V区基因，从其中一个供体中鉴定出一个新的多态性J(kappa)2基因片段。为了解释疾病相关的体细胞突变CD5(+) B细胞的频繁发生与正常CD5(+) B细胞的低发生率或不存在体细胞突变之间的差异，我们推测CD5(+) B细胞通常不参与生发中心反应，但如果它们偶尔这样做，它们可能会增加参与自身免疫性疾病或B细胞恶性肿瘤的风险。
B cells expressing the CD5 cell surface antigen are involved in certain B cell malignancies and autoimmune diseases, From studies in the mouse, it emerged that CD5(+) B cells represent a separate lineage of B lymphocytes that, in contrast to conventional (CD5(-)) B cells, are not driven into T cell-dependent immune responses in which rearranged variable (V) region genes are diversified by somatic hypermutation. Against this background it came as a surprise that human disease-involved CD5-positive autoreactive B cells as well as B cell chronic lymphocytic leukemias can harbor somatically mutated V region genes, Recent V gene analyses on CD5(+) B cells in healthy adults did not give rise to a clear picture about the fraction of somatically mutated among all CD5(+) B cells, In this work we used a molecular single-cell analysis to determine reliably the frequency of mutated CD5(+) B cells in healthy humans: single, kappa light chain-expressing CD5(+) peripheral blood B cells were isolated by flow cytometry, and rearranged V kappa genes were amplified by PCR, From one donor, CD5(+)CD19(+) B cells were analyzed, Since CD5(+) B cells were found among IgM(+)IgD(+) and IgM(+)IgD(-) cells (but almost not among class-switched cells) from two other donors, individual cells corresponding to these IgM-expressing subsets were investigated separately, The sequence analysis of rearranged V-kappa genes revealed that most if not all CD5(+) B cells in healthy humans carry unmutated V region genes, From one of the donors, a novel polymorphic J(kappa)2 gene segment was identified. To explain the discrepancy between the frequent occurrence of disease-associated somatically mutated CD5(+) B cells and the low incidence or absence of somatic mutation in normal CD5(+) B cells, we speculate that CD5(+) B cells usually do not participate in germinal center reactions, but if they occasionally do so, they may be at an increased risk to become involved in autoimmune diseases or B cell malignancies.