Fleit H B, Lane A P, Watson T J, Kuhnle M, Lane B P
Department of Pathology, State University of New York, Stony Brook.
Lab Invest. 1987 Dec;57(6):699-707.
Fc Receptors (FcR) mediate the binding and uptake by polymorphonuclear leukocytes (PMN) of antibody-coated particles and soluble immune complexes. We have studied Fc-mediated endocytosis by PMN ultrastructurally using a gold-conjugated monoclonal antibody (3G8) to block or to mark the location of FcR. Phagocytosis of antibody-coated erythrocytes (EIgG) was initiated rapidly after binding to discrete foci on the PMN plasma membrane. After the phagocytosis of EIgG, we examined the distribution of FcR remaining on the PMN plasma membrane. 3G8-Colloidal gold continued to bind to PMN after ingestion of up to three EIgG, demonstrating that all PMN FcR are not utilized during a brief phagocytic event. The endocytosis of soluble immune complexes was examined by labeling plasma membrane-bound rabbit immune complexes with goat anti-rabbit IgG conjugated to colloidal gold. Gold was found in clusters randomly distributed over the plasma membrane at 4 degrees C. When cells were warmed to 37 degrees C, numerous endocytic vesicles were observed as early as 2.5 minutes after warming. After 30 minutes at 37 degrees C, large vesicles, 1 micron in diameter, were found to contain 20 to 30 gold particles. The endocytosis of 3G8 was also examined using colloidal gold. After binding of 3G8-gold at 4 degrees C, clusters of large vesicles, up to 2 micron in diameter, were rapidly formed at 37 degrees C.
Fc受体（FcR）介导多形核白细胞（PMN）对抗体包被颗粒和可溶性免疫复合物的结合与摄取。我们使用金偶联单克隆抗体（3G8）在超微结构水平上研究了PMN的Fc介导的内吞作用，以阻断或标记FcR的位置。抗体包被的红细胞（EIgG）与PMN质膜上的离散位点结合后，迅速引发吞噬作用。吞噬EIgG后，我们检查了PMN质膜上剩余FcR的分布。摄取多达三个EIgG后，3G8-胶体金继续与PMN结合，表明在短暂的吞噬事件中并非所有PMN FcR都被利用。通过用胶体金偶联的山羊抗兔IgG标记质膜结合的兔免疫复合物来检查可溶性免疫复合物的内吞作用。在4℃时，金簇随机分布在质膜上。当细胞升温至37℃时，早在升温后2.5分钟就观察到大量内吞小泡。在37℃下30分钟后，发现直径为1微米的大泡含有20至30个金颗粒。还使用胶体金检查了3G8的内吞作用。在4℃下结合3G8-金后，在37℃迅速形成直径达2微米的大泡簇。
