C3是补体系统中含量最高,功能最复杂的成份,也是连接经典途径与替代途径的枢纽。完整的 C 3分子蕴藏着多种功能结构,被 C 3转化酶分解之后,便逐次暴露出来,表现重要的生物学功能。C3b是补体系统最重要的活性片段,既是机体防御屏障的要素,又是某些重要的补体酶的组成部份。新生的 C3b 一方面共价结合于微生物或免疫复合物(IC)另一方面 C3 is the most abundant and most complex component of the complement system, as well as a link to the classic and alternative approaches. The intact C 3 molecule contains a variety of functional structures that, after being broken down by C 3 -converting enzymes, are exposed one after the other and exhibit important biological functions. C3b is the most important active fragment of the complement system, both as an integral part of the body’s defense barrier and as part of some important complement enzymes. The nascent C3b is covalently bound on the one hand to the microbe or immune complex (IC) on the other hand