Fujita T, Shinkai Y, Inoue T, Tamura N
Department of Immunology, University of Tsukuba, Ibaraki-ken, Japan.
Immunology. 1988 Jul;64(3):369-74.
Decay-accelerating factor (DAF), a membrane protein that regulates the complement system, was purified to homogeneity from lymphoblastoid (Raji) cells (DAF-R). It exhibited almost the same molecular weight as DAF from stroma of erythrocytes (DAF-S). Purified DAF-R, which could be reincorporated into cell membranes, accelerated the decay of the C3 convertases, in both the classical (C4b2a) and the alternative (C3bBb) pathways. This activity was completely inhibited by a monoclonal anti-DAF antibody, 1C6. From these results, DAF-R and DAF-S can not be distinguished; however, the decay-accelerating activity of DAF-R was much higher than that of DAF-S. 1C6 enhanced the binding of C3 to Raji cells by incubating with six purified components of the alternative pathway, whereas it did not induce the killing of Raji cells after a short incubation period. When antibodies against Raji cells were added to the above system, the blocking of DAF activity by 1C6 resulted in efficient killing of Raji cells by autologous complement. From these results, it is clear that DAF on nucleated cells plays an important role in protecting these cells from the damage caused by autologous complement.
衰变加速因子（DAF）是一种调节补体系统的膜蛋白，已从淋巴母细胞样（Raji）细胞（DAF-R）中纯化至同质状态。它的分子量与红细胞基质中的DAF（DAF-S）几乎相同。纯化后的DAF-R可重新整合到细胞膜中，能加速经典途径（C4b2a）和替代途径（C3bBb）中C3转化酶的衰变。这种活性被单克隆抗DAF抗体1C6完全抑制。从这些结果来看，DAF-R和DAF-S无法区分；然而，DAF-R的衰变加速活性远高于DAF-S。1C6与替代途径的六种纯化成分一起孵育时，增强了C3与Raji细胞的结合，而在短时间孵育后它并未诱导Raji细胞的杀伤。当将抗Raji细胞的抗体添加到上述系统中时，1C6对DAF活性的阻断导致自体补体对Raji细胞的有效杀伤。从这些结果可以清楚地看出，有核细胞上的DAF在保护这些细胞免受自体补体造成的损伤方面起着重要作用。
