Tornberg U C, Holmberg D
Department of Cell and Molecular Biology, University of Umeå, Sweden.
EMBO J. 1995 Apr 18;14(8):1680-9. doi: 10.1002/j.1460-2075.1995.tb07157.x.
Analyses of VHDJH rearrangements isolated from murine peritoneal B-1a cells (CD5+, IgMhi, B220lo), peritoneal B-1b cells (CD5-, IgMhi, B220lo), and conventional splenic B cells provide evidence that a unique repertoire of VH regions is displayed by each of these B-cell subsets. The B-1a subset is characterized by a low N-region diversity, by a high frequency of sequence homologies in the VH-D and D-JH junctions, and by a limited exonuclease nibbling of the terminals of the joining gene segments. Through expansion in ageing mice, B-1a clones with these properties are favoured. B-1b cells are similar to conventional B-2 cells with respect to N-region diversity, but are unique in terms of D gene expression. Thus, while most murine pre-B and B cells preferentially use DSP and DFL gene segments in a given reading frame (RF1), B-1b cells frequently express D genes in another reading frame (RF2). Together, these findings provide structural evidence for a model where B-1a, B-1b and B-2 cells are produced by separate progenitors that are active at different stages of ontogeny.
对从小鼠腹膜B-1a细胞（CD5⁺、IgM高、B220低）、腹膜B-1b细胞（CD5⁻、IgM高、B220低）和传统脾B细胞中分离出的VHDJH重排进行分析，结果表明这些B细胞亚群各自展示了独特的VH区域库。B-1a亚群的特征在于N区多样性低、VH-D和D-JH连接处序列同源性频率高，以及连接基因片段末端的外切酶蚕食有限。通过在衰老小鼠中的扩增，具有这些特性的B-1a克隆受到青睐。B-1b细胞在N区多样性方面与传统B-2细胞相似，但在D基因表达方面具有独特性。因此，虽然大多数小鼠前B细胞和B细胞在给定读框（RF1）中优先使用DSP和DFL基因片段，但B-1b细胞经常在另一个读框（RF2）中表达D基因。这些发现共同为一个模型提供了结构证据，即B-1a、B-1b和B-2细胞由在个体发育不同阶段活跃的不同祖细胞产生。
