Matsuo T, Kimoto M, Sakaguchi N
Department of Immunology, Saga Medical School, Japan.
J Immunol. 1991 Mar 1;146(5):1584-90.
The B cell-specific mb-1 gene was recently reported to encode a putative surface glycoprotein with CD3-like structural properties. Hombach et al. suggested and presented evidence to show that this mb-1 gene encodes the 34-kDa membrane glycoprotein (B34 or IgM-alpha) associated with IgMR molecule. To identify the mb-1 gene product directly in B cells, affinity-purified MB-1-specific antibody was prepared by immunization of rabbits with synthetic MB-1 oligopeptide. Immunoprecipitation in combination with two-dimensional diagonal gel electrophoresis analysis revealed that this antibody detected a B cell-specific surface glycoprotein that is very similar to the IgM-alpha (B34) protein described by Hombach et al. However, MB-1 protein exists usually as the monomeric form on the surface of B cells, in contrast to IgM-alpha, which was detected as the dimeric (IgM-alpha/IgM-alpha or IgM-alpha/Ig-beta) protein. We also found that MB-1 protein is already expressed on the sIgM- pre-B cell lymphoma, which might suggest an alternative functional role of this B cell-specific MB-1 protein in B cell differentiation. The molecular identity of MB-1 protein and IgM-alpha (B34) is discussed.
最近有报道称，B细胞特异性mb-1基因编码一种具有类似CD3结构特性的假定表面糖蛋白。洪巴赫等人提出并提供证据表明，该mb-1基因编码与IgMR分子相关的34 kDa膜糖蛋白（B34或IgM-α）。为了在B细胞中直接鉴定mb-1基因产物，用合成的MB-1寡肽免疫兔子制备了亲和纯化的MB-1特异性抗体。免疫沉淀结合二维对角线凝胶电泳分析表明，该抗体检测到一种B细胞特异性表面糖蛋白，它与洪巴赫等人描述的IgM-α（B34）蛋白非常相似。然而，与被检测为二聚体（IgM-α/I gM-α或IgM-α/I g-β）蛋白的IgM-α不同，MB-1蛋白通常以单体形式存在于B细胞表面。我们还发现，MB-1蛋白已在sIgM-前B细胞淋巴瘤中表达，这可能表明这种B细胞特异性MB-1蛋白在B细胞分化中具有另一种功能作用。本文讨论了MB-1蛋白与IgM-α（B34）的分子同一性。
