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

替代补体途径的激活不依赖于形成C3转换酶的抗原-抗体复合体。不同物种的交替途径不同，其识别功能的特异性不同。因此，人的替代途径是由兔红细胞激活的，而兔的替代途径是由人的红细胞激活的，显然该替代途径不被同源红细胞激活。因此，替代途径的组成部分区分同种和异种红细胞。在这个项目中，我试图确定在区分过程中起作用的组件。从人血和兔血中提纯了构成替代途径的6种成分(C3、B、D、P、H和I因子)。用相应的兔组分取代重组混合物，并用兔和人红细胞测定了取代的重组混合物的溶血活性。结果表明，C3是异种红细胞识别过程中的主要参与者，由于红细胞膜上的某些成分可能也参与了替代途径所表现出的识别过程，因此我试图对该成分进行鉴定。红细胞膜蛋白中最可能的候选蛋白似乎是DAF(C3，C5-转换酶的衰变加速因子)。用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。纯化的DAF对同源C3的亲和力高于对异源C3的亲和力，表明DAF参与了识别过程。

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.