Recognition mechanism of heterologous erythrocytes by the alternative pathway of complement.

补体旁路途径的激活不依赖于形成 C3 转化酶的抗原-抗体复合物。不同物种的替代途径因其识别功能的特异性而不同。因此，人旁路途径是由兔红细胞激活的，而兔旁路途径是由人红细胞激活的；很明显，同源红细胞不激活旁路途径。因此，旁路途径的成分区分同源红细胞和异源红细胞。在这个项目中，我试图确定在区分过程中发挥作用的组件。构成旁路途径的所有六种成分（C3、B、D、P、H 和 I 因子）均从人和兔的血液中纯化。用相应的兔成分替代重构混合物，并用兔和人红细胞测量替代的重构混合物的溶血活性。结果表明，C3是异源红细胞识别过程的主要参与者。由于红细胞膜上的某些成分也应该负责旁路途径所表现出的识别过程，因此我试图识别该成分。红细胞膜蛋白中最有可能的候选者似乎是 DAF（C3、C5 转化酶的衰变加速因子）。通过为本项目开发的方法，从相应的红细胞膜中分离出人和兔的 DAF。由此纯化的DAF对同源C3显示出比对异源C3更高的亲和力；表明DAF是识别过程的参与者。

Activation of the alternative complement pathway is independent of antigen-antibody complex for formation of C3 convertase. The alternative pathway of various species differs in the specificity of their recognition function. Thus, human alternative pathway is activated by rabbit erythrocytes while rabbit alternative pathway is activated by human erythrocytes; it is evident that the alternative pathway is not activated by homologous erythrocytes. Therefore, components of the alternative pathway distinguish between homologous and heterologous erythrocytes. In this project, I tried to determine the components that play a role on the distinguishing process. All of the six components constituting the alternative pathway (C3, B, D, P, H and I factors)were purified from both of human and rabbit bloods. The reconstitution mixture were substituted with the corresponding rabbit components and the hemolytic activities of the substituted reconstitution mixtures were measured with rabbit and human erythrocytes. The results indicated that C3 was the major participant in the recognition process of heterologous erythrocytes.Since some components on erythrocyte membranes should be also responsible for the recognition process exhibited by the alternative pathway, I tried to identify the component. The most likely candidate among erythrocyte membrane proteins seemed to be DAF ( decay-accelerating factor of C3, C5-convertases ). Human and rabbit DAF's were isolated from the corresponding erythrocyte membranes by the methods developed for this project. DAF thus purified showed higher affinity to homologous C3 than to heterologous C3; indicating that DAF is a participant in the recognition process.