Identification of a 145,000 Mr membrane protein as the C3d receptor (CR2) of human B lymphocytes.
Identification of a 145,000 Mr membrane protein as the C3d receptor (CR2) of human B lymphocytes.
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DOI：
10.1073/pnas.81.3.881
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发表时间：
1984-02
影响因子：
11.1
通讯作者：
J. Weis;T. Tedder;D. Fearon
中科院分区：
文献类型：
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作者：
J. Weis;T. Tedder;D. Fearon
人B淋巴细胞的C3 d受体（CR2）介导免疫复合物与这些细胞的结合，所述免疫复合物已激活补体系统并携带C3、iC 3 B、C3 d、g和C3 d的片段。先前描述为被单克隆抗体HB-5识别并显示仅由B淋巴细胞和B类淋巴母细胞系（如Raji）表达的145，000 Mr膜蛋白被评估其与CR 2的可能同一性。用HB-5和山羊F（ab '）2抗小鼠IgG（GaM）处理Raji细胞，降低了这些细胞与带有130，000个iC 3b或C3 d分子的绵羊红细胞（E）中间体形成ROBLESS的能力，而单独用单克隆抗体处理则没有效果。外周血B淋巴细胞结合EC 3d的能力同样被HB-5和GaM的组合抑制。HB-5可能与CR2上不同于配体结合位点的位点相互作用的可能性允许直接分析HB-5抗原与C3片段结合的能力。将HB-5已结合的含蛋白A的金黄色葡萄球菌颗粒与Raji细胞和B淋巴细胞的去污剂裂解物在已显示仅与145，000 Mr抗原结合相关的条件下孵育。这些携带HB-5和来自任一细胞类型的抗原的颗粒显示出特异性粘附于EiC 3b和EC 3d，表明HB-5抗原从携带CR2的细胞转移到S.金黄色葡萄球菌颗粒导致颗粒获得CR2功能。另外，HB-5抑制Raji细胞与EC 3b形成细胞骨架的能力相对较弱，而S.带有与EC 3b结合的免疫吸附的HB-5抗原的金黄色葡萄球菌颗粒表明，CR 1阴性Raji细胞的C3 b结合功能存在于CR2中，而不是在其他膜蛋白中。
The C3d receptor (CR2) of human B lymphocytes mediates the binding to these cells of immune complexes that have activated the complement system and bear the fragments of C3, iC3b, C3d,g, and C3d. A 145,000 Mr membrane protein previously described as being recognized by the monoclonal antibody HB-5 and shown to be expressed only by B lymphocytes and B lymphoblastoid cell lines, such as Raji, was assessed for its possible identity as CR2. Treatment of Raji cells with HB-5 and goat F(ab')2 anti-mouse IgG (GaM) diminished the capacity of these cells to form rosettes with sheep erythrocyte (E) intermediates bearing 130,000 molecules of iC3b or C3d, whereas treatment with the monoclonal antibody alone had no effect. The capacity of peripheral blood B lymphocytes to bind EC3d was similarly inhibited by the combination of HB-5 and GaM. The possibility that HB-5 may interact with a site on CR2 that is distinct from the ligand binding site permitted the direct analysis of the capacity of the HB-5 antigen to bind to the C3 fragments. Protein A-containing Staphylococcus aureus particles to which HB-5 had been bound were incubated with detergent lysates of Raji cells and B lymphocytes under conditions that had been shown to be associated only with the binding of the 145,000 Mr antigen. These particles bearing HB-5 and antigen derived from either cell type were shown to adhere specifically to EiC3b and EC3d, demonstrating that transfer of the HB-5 antigen from CR2-bearing cells to S. aureus particles led to the acquisition of CR2 function by the particles. The additional findings that the relatively weak capacity of Raji cells to form rosettes with EC3b was inhibited by HB-5 and that the S. aureus particles bearing immunoadsorbed HB-5 antigen bound to EC3b indicated that the C3b-binding function of the CR1-negative Raji cell resides in CR2, rather than in other membrane proteins.