Frequency and characterization of phenotypic Ig heavy chain allelically included IgM-expressing B cells in mice
Frequency and characterization of phenotypic Ig heavy chain allelically included IgM-expressing B cells in mice
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DOI：
10.4049/jimmunol.164.2.893
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发表时间：
2000-01-15
影响因子：
4.4
通讯作者：
Cumano, A
中科院分区：
文献类型：
--
作者：
Barreto, V;Cumano, A
igg H链（IgH）等位基因排斥仍然是一个令人困惑的话题。在这里，我们解决以下问题：在正常小鼠中是否存在表型等位基因包含的细胞，如果存在，频率是多少？通过双胞浆内染色评估杂合小鼠分选细胞中两种IgM同种异体的表达，双表达频率为10(4)个脾B细胞中有1个。这些数据是通过对双表达者进行单细胞（或克隆）PCR获得的高重排等位基因的直接测序得到的，通常，这些细胞中有一个重排的J558 V-H基因，而在另一个等位基因中，使用了一个d -近端V-H基因。有趣的是，双表达子重排了具有相似CDR3长度的IgH等位基因。这些结果表明，与kappa L链和TCR β链相反，IgH等位基因的排除是一个极其严格的机制的结果。我们讨论了两种不相互排斥的IgH双表达子起源情况：1)当第一个有效重排的等位基因无法形成前bcr时，包含IgH等位基因的细胞出现；双表达子可能是这个群体的一个子集，在常规的L链重排后，两个IgH都在表面表达；2) IgH等位基因同步重排。
Ig H chain (IgH) allelic exclusion remains a puzzling topic. Here, we address the following question: Do phenotypic IgH allelically included cells exist in normal mice and, if so, at what frequency? Sorted cells from heterozygous mice were evaluated for the expression of both IgM allotypes by double intracytoplasmic stainings, Dual expressors were found at a frequency of 1 in 10(4) splenic B cells. These data were confirmed by direct sequencing of IgH-rearranged alleles obtained after single cell (or clone) PCR on dual expressors, Typically, these cells have one rearranged J558 V-H whereas, in the other allele, a D-proximal V-H gene is used. Interestingly, dual expressors have rearranged IgH alleles with similar CDR3 lengths. These results show that, in contrast to the kappa L chain and the TCR beta-chain, IgH allelic exclusion is the result of an extremely stringent mechanism. We discuss two non-mutually exclusive scenarios for the origin of IgH dual expressors: 1) IgH allelically included cells arise when the first allele to rearrange productively is unable to form a pre-BCR; dual expressors could be a subset of this population in which, upon conventional L chain rearrangement, both IgH are expressed at the surface; and 2) synchronous rearrangement of the IgH alleles.