Nicholson I C, Brisco M J, Zola H
Department of Clinical Immunology, Flinders Medical Centre, Bedford Park, Australia.
J Immunol. 1995 Feb 1;154(3):1105-13.
To clarify the phenotype of memory B lymphocytes, we have determined the frequency of somatic hypermutations in purified tonsil B cell populations. Our particular interest was the controversial question of whether any memory B-cells express IgD. Ig heavy chain gene rearrangements that used the nonpolymorphic VH6 gene were amplified by PCR, cloned, and sequenced. All eight sequences obtained from the surface IgD (sIgD)-negative fraction contained point mutations, with frequency of one mutation in every 24 bases of sequence. In contrast, only 4 of 12 sequences obtained from the sIgD-positive fraction contained point mutations, with a mutation frequency of one in 600. This frequency was similar to that found for cord blood B cells (one in 550), a population that does not contain memory B cells. These results indicate that although memory B cells are present in the sIgD-negative fraction, no memory cells can be detected in the sIgD-positive fraction of tonsil B lymphocytes.
为了阐明记忆B淋巴细胞的表型，我们测定了纯化的扁桃体B细胞群体中体细胞超突变的频率。我们特别感兴趣的是一个有争议的问题，即是否有任何记忆B细胞表达IgD。使用非多态性VH6基因的Ig重链基因重排通过PCR进行扩增、克隆和测序。从表面IgD（sIgD）阴性部分获得的所有八个序列都包含点突变，序列中每24个碱基就有一个突变。相比之下，从sIgD阳性部分获得的12个序列中只有4个包含点突变，突变频率为600分之一。这个频率与脐血B细胞（550分之一）的频率相似，脐血B细胞群体中不包含记忆B细胞。这些结果表明，虽然记忆B细胞存在于sIgD阴性部分，但在扁桃体B淋巴细胞的sIgD阳性部分中未检测到记忆细胞。
