Restriction in IgM expression--I. The VH regions of equine anti-lactose antibodies.
Restriction in IgM expression--I. The VH regions of equine anti-lactose antibodies.
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IgM 表达限制--I．
DOI：
10.1016/0161-5890(80)90181-9
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发表时间：
1980
影响因子：
3.6
通讯作者：
Karush,F
中科院分区：
文献类型：
--
作者：
Rodwell,JD;Karush,F
在诱导的IgM应答中，IgG应答的特征性亲和力成熟现象通常是有限的或不存在。这一观察结果导致提出IgM仅限于生殖系V区基因的表达，而IgG利用生殖系基因及其体细胞变体。本研究用等电聚焦分析法比较了6匹马抗乳糖IgM抗体的VH区。这六种模式在它们的复杂性（约30条带）、带的等电点和它们的相对强度方面几乎相同。这一发现是根据生殖系限制的假设预测的。正常马IgM和抗SIII IgM的VH区表现出相似的复杂性，但不同的强度分布。平行的复杂性归因于通过IEF观察到的大量（例如1350个）带电氨基酸的不同组合物的可区分的等电点的数目的简并性。基于次级（记忆）B细胞不参与IgM产生的假设，提出了IgM抗体表达中的种系限制的细胞模型。由此产生的对IgM初级反应的限制排除了利用体细胞变异产生的扩展谱系，因为这些变异无法进行足够的克隆扩增以产生足够数量的产生IgM的浆细胞。
The phenomenon of affinity maturation, characteristic of the IgG response, is generally limited or absent in the induced IgM response. This observation has led to the proposal that IgM is restricted to the expression of germ-line V region genes whereas IgG utilizes both germ-line genes and their somatic variants. In this study the VHregions prepared from purified anti-lactose IgM antibody of six horses were compared by analytical isoelectric focusing (IEF). The six patterns were virtually identical with respect to their complexity (about 30 bands), the isoelectric points of the bands and their relative intensities. This finding is predicted from the assumption of germ-line restriction. The VHregions from normal equine IgM and antiSIII IgM exhibited a similar complexity but different intensity distributions. The parallel complexity is attributed to the degeneracy of the number of distinguishable isoelectric points observable by IEF for a large number (e.g. 1350) of different compositions of charged amino acids. A cellular model is proposed for the germ-line restriction in the expression of IgM antibody based on the assumption that secondary (memory) B cells are not involved in IgM production. The consequent limitation to a primary response for IgM precludes the utilization of the expanded repertoire generated by somatic variants because these variants are unable to undergo sufficient clonal expansion to yield adequate numbers of IgM-producing plasma cells.