Zeitz H J, Zeff R A, Gewurz H, Lint T F
J Immunol. 1983 Jun;130(6):2809-13.
In addition to its role in hemolysis and host defense against Neisseria infection, the eighth component of human complement (C8) is one of several plasma proteins that are C5b67-inhibitors (C5b67-INH). The recent identification in our laboratory of two new families with hereditary deficiency of C8 provided an opportunity to study further the role of C8 as a C5b67-INH. Based on mixing and reconstitution experiments, the deficiency of C8 seemed to be due to a selective lack of the C8 beta-chain in one family and the C8 alpha-gamma subunit in the other family. Sera from individuals homozygous for the C8 abnormality were substantially deficient in C5b67-INH activity as well as totally deficient in hemolytic activity. Sera from control individuals possessed approximately 2500 C5b67-INH U/ml, whereas sera from the C8-deficient individuals had markedly depressed C5b67-INH activity, with a mean of only 428 U/ml. C5b67-INH activity was completely reconstituted in C8-deficient serum by the addition of purified human C8. We conclude that C8 constitutes the substantial majority of the C5b67-INH activity of normal human serum.
除了在溶血和宿主抵御奈瑟菌感染中发挥作用外，人补体的第八成分（C8）是几种血浆蛋白之一，属于C5b67抑制剂（C5b67-INH）。最近我们实验室鉴定出两个患有遗传性C8缺乏症的新家族，这为进一步研究C8作为C5b67-INH的作用提供了机会。基于混合和重组实验，C8缺乏似乎是由于一个家族中选择性缺乏C8β链，而另一个家族中缺乏C8α-γ亚基。C8异常纯合个体的血清中C5b67-INH活性严重缺乏，溶血活性也完全缺乏。对照个体的血清中C5b67-INH活性约为2500 U/ml，而C8缺乏个体的血清中C5b67-INH活性明显降低，平均仅为428 U/ml。通过添加纯化的人C8，C8缺乏血清中的C5b67-INH活性得以完全恢复。我们得出结论，C8构成了正常人血清中C5b67-INH活性的绝大部分。
