Hombach J, Tsubata T, Leclercq L, Stappert H, Reth M
Max-Planck-Institut für Immunbiologie, Freiburg, FRG.
Nature. 1990 Feb 22;343(6260):760-2. doi: 10.1038/343760a0.
The antigen receptors on mature B lymphocytes are membrane-bound immunoglobulins of the IgM and IgD classes whose cross-linking by polyvalent antigens results in B-cell proliferation and differentiation. How these membrane-bound immunoglobulin chains, which lack a cytoplasmic tail, generate a cell activation signal is not at present known. We now show that the IgM molecule is non-covalently associated in the membrane of B cells with two proteins of relative molecular mass 34,000 (Mr 34 K; IgM-alpha) and 39 K (Ig-beta) which form a disulphide-linked heterodimer. Surface expression of IgM seems to require the formation of an appropriate complex between IgM and the heterodimer. A transfection experiment indicates that IgM-alpha is the product of mb-1, a B-cell specific gene encoding a transmembrane protein with sequence homology to proteins of the T-cell antigen receptor-CD3 complex.
成熟B淋巴细胞上的抗原受体是IgM和IgD类的膜结合免疫球蛋白，其通过多价抗原交联导致B细胞增殖和分化。目前尚不清楚这些缺乏胞质尾的膜结合免疫球蛋白链如何产生细胞激活信号。我们现在表明，IgM分子在B细胞膜中与相对分子质量为34,000（Mr 34K；IgM-α）和39K（Ig-β）的两种蛋白质非共价结合，这两种蛋白质形成二硫键连接的异二聚体。IgM的表面表达似乎需要IgM与异二聚体之间形成适当的复合物。转染实验表明，IgM-α是mb-1的产物，mb-1是一种B细胞特异性基因，编码一种与T细胞抗原受体-CD3复合物的蛋白质具有序列同源性的跨膜蛋白。
