APOPTOSIS AND COMPLEMENT-STUDIES ON THE MECHANISM OF COMPKEMENT ACTIVATION AND THE BIOLOGICAL SIGNIFICANCE

我们研究了凋亡细胞激活自身补体的机制，以及补体激活在巨噬细胞清除凋亡细胞中的生物学意义。凋亡细胞中自体补体途径的激活物。同源活细胞不存在补体激活。我们观察到人类凋亡细胞激活自体补体途径，提示在凋亡细胞上出现了一种新的补体激活剂。为了鉴定这种新的激活剂，Jurkat Y细胞系被允许分裂，其细胞蛋白经SDS-PAGE分析，然后用人血清作为补体来源。C3b沉积的50 KDa蛋白发生完全激活，表明存在能够激活自体补体的50 KDa分子。在活细胞膜部分检测到相同的分子。基于这些数据，我们提出了50 KDa激活蛋白I…结论1.更多的S定位于活细胞的膜部分，并在凋亡时暴露于细胞表面。新型补体激活剂的分离研究目前正在进行中。补体激活对巨噬细胞吞噬细胞的影响。我们发现，血清处理的凋亡细胞被IC3b标记，这是一种被称为调理素的物质。这提示IC3b可能与巨噬细胞表面的CR3相互作用，促进巨噬细胞对凋亡细胞的吞噬，IC3b包被的凋亡细胞被巨噬细胞吞噬的速度明显快于包被ic3b的巨噬细胞。抗ic6b抗体和抗CR3抗体抑制了IC6b包被的巨噬细胞对IC6b包被的凋亡细胞的吞噬作用，提示IC3b可能与巨噬细胞上的CR3相互作用，促进吞噬细胞对凋亡细胞的清除。因此，补体不仅是一种宿主防御系统，而且是一种清除细胞的生理系统，如凋亡细胞。较少

We investigated the mechanism of autologous complement activation by apoptotic cells and biological significance of complement activation in the clearance of apoptotic cells by macrophages.1. Activator of the autologous complement pathway in apoptotic cells. Complement activation does not occur on homologous live cells.We observed the activation of the autologous complement pathway by human apoptotic cells, suggesting the appearance of a novel complement activator on apoptotic cells.To characterize the novel activator, Jurkat Y cell line was allowed to spoptosis and its cell proteins were subjected to SDS-PAGE and subsequently treated with human serum as a source of complement.Complemnt activation occurred on a 50 KDa protein, which was become deposited with C3b, suggesting the presence of 50 KDa molecule capable of activating autologous complement.The same molecule was detected in the membrane fraction of live cells. Based on these data, we proposed that the 50 KDa activator protein i … More s located in the membrane fraction of live cells and become exposed to cell surface upon apoptosis.Studies on the isolation of the novel complement activator are now in progress.2. The effect of complement activation upon phagocytosis of qpoptotic cells by macrophages.We found that serum-treated apoptotic cells were labeled with ic3b, which is known as an opsonin. This suggested that ic3b on apoptotic cells might interact with CR3 of macrophages and promote the phagocytosis of apoptotic cells.The ic3b-coated apoptotic cells were found to be phagocytosed much more quickly than ic3b-noncoated cells by macrophages.The phagocytosis of ic6b-coated apoptotic cells by macrophages was found to be inhibited by anti-ic6b antibodies and anti-CR3, indicating that ic3b on apoptotic cells should interact with CR3 on macrophages and promote the clearance of apoptotic cells by phagocytes.Thus, complement is not only a host defense system but also a physiological system to remove unnecessary cells, such as apoptotic cells. Less