Fearon D T
J Exp Med. 1980 Jul 1;152(1):20-30. doi: 10.1084/jem.152.1.20.
A human erythrocyte membrane glycoprotein of 205,000 mol wt (gp205) has been identified as the C3b receptor of the erythrocyte, polymorphonuclear leukocyte (PMN), B lymphocyte, and monocyte. Initially, gp205 was sought and characterized as a constituent of the human erythrocyte membrane that can impair activation of the alternative complement pathway by inducing loss of function of the properdin-stabilized amplification C3 convertase (C3b,Bb,P) through displacement of Bb from C3b and by promoting cleavage-inactivation of C3b by C3b inactivator. These inhibitory activities of gp205 suggested that this membrane glyeoprotein had an affinity for C3b and prompted an analysis of its possible identity as the C3b receptor of human peripheral blood cells. The F(ab')2 fragment of rabbit IgG anti-gp205 inhibited the formation of rosettes with sheep EC3b of human erythroeytes, B lymphocytes, monocytes and PMN in a dose-response manner; the 50 percent inhibitory doses were 0.13/mug/ml, 0.90 mug/ml, 1.25 mug/ml, and 1.20 mug/ml of F(ab')2, respectively. Anti-gp205 did not impair the formation of rosettes by monocytes and B lymphocytes with sheep EC3bi or with EC3d. Scatchard analysis of the number of specific (125)I-F(ab')(2) anti-gp205 binding sites/cell revealed 950 sites/erythrocyte, 21,000 sites/cell of B lymphocyte preparation, 57,000 sites/PMN, and 48,000 sites/monocyte, indicating that the higher concentrations of antibody that had been required for inhibition of rosette formation by the nucleated cells reflected larger numbers of receptors on these cells. Direct evidence for the identity of gp205 as the C3b receptor of the four cell types was obtained when detergent-solubilized membrane proteins of the surface-radioiodinated cells were reacted with anti- gp205 and the immunoprecipitate was analyzed by polyacrylamide gel electrophoresis in the presence of sodium dodecyl sulfate. In each instance, the antigenic material reacting with anti-gp205 represented a single protein with an apparent 205,000 mol wt. Thus, gp205 is the C3b receptor of human erythrocytes, PMN, B lymphocytes, and monocytes.
一种分子量为205,000的人红细胞膜糖蛋白（gp205）已被确定为红细胞、多形核白细胞（PMN）、B淋巴细胞和单核细胞的C3b受体。最初，gp205被寻找并鉴定为人类红细胞膜的一种成分，它可以通过将Bb从C3b上置换下来，并通过促进C3b灭活剂对C3b的裂解失活，来损害替代补体途径的激活，从而导致备解素稳定的C3转化酶（C3b,Bb,P）功能丧失。gp205的这些抑制活性表明这种膜糖蛋白对C3b具有亲和力，并促使人们分析它是否可能是人外周血细胞的C3b受体。兔抗gp205 IgG的F(ab')2片段以剂量依赖方式抑制人红细胞、B淋巴细胞、单核细胞和PMN与绵羊EC3b形成玫瑰花结；50%抑制剂量的F(ab')2分别为0.13μg/ml、0.90μg/ml、1.25μg/ml和1.20μg/ml。抗gp205并不损害单核细胞和B淋巴细胞与绵羊EC3bi或EC3d形成玫瑰花结。对特异性(125)I-F(ab')2抗gp205结合位点/细胞数量的Scatchard分析显示，红细胞为950个位点/细胞，B淋巴细胞制剂为21,000个位点/细胞，PMN为57,000个位点/细胞，单核细胞为48,000个位点/细胞，这表明有核细胞抑制玫瑰花结形成所需的抗体浓度较高反映了这些细胞上有更多的受体。当用抗gp205与表面放射性碘化细胞的去污剂溶解膜蛋白反应，并在十二烷基硫酸钠存在下通过聚丙烯酰胺凝胶电泳分析免疫沉淀物时，获得了gp205作为四种细胞类型的C3b受体的直接证据。在每种情况下，与抗gp205反应的抗原物质都代表一种表观分子量为205,000的单一蛋白质。因此，gp2是人类红细胞、PMN、B淋巴细胞和单核细胞的C3b受体。
