Kitamura H, Tsuboi M
Department of Immunology, Center for Adult Diseases, Osaka, Japan.
Immunology. 1989 Feb;66(2):264-9.
A serum factor, which inhibits haemolysis of the buffer control used in a C3 haemolytic assay, was found in a C3-deficient subject (C3D). Since the buffer control consisted of EAC142, C5 and C6-9 reagent (C6-9R, prepared by treatment of guinea-pig serum with KSCN and hydrazine hydrate), the factor seems to be an inhibitor of C3-independent immune haemolysis. Gel filtration and CM cellulose column chromatography of C3D serum suggested that the inhibitor may be C8. The inhibition was not observed in C8-depleted C3D serum. Furthermore, isolated C8 was found to inhibit haemolysis of EAC142 by C5 and C6-9R in a dose-dependent fashion. Thus, C8 was found to be an inhibitor of C3-independent immune haemolysis in the assay. Further studies revealed that C8 also inhibits haemolysis of EAC142 by C3, C5 and C6-9R (C3 assay system) or that of EAC1423 by C5 and C6-9R (C5 assay system), indicating that C3 or C5 haemolytic activity can be underestimated by the presence of C8 in a sample. C8 did not inhibit haemolysis in the assay system when isolated C6-C9 of human origin were used, but did inhibit haemolysis when isolated C6-C9 of guinea-pig origin was used instead of C6-9R. Thus, it was suggested that the incompatibility of human C8 with guinea-pig C6-C9 might be responsible for this phenomenon. Additional experiments for the mechanism clearly showed that human C8 inhibits the haemolysis of EAC1-7 (EA bearing human C1-C5 and guinea-pig C6 and C7) by guinea-pig C8 and C9 by binding to EAC1-7 prior to guinea-pig C8.
在一名C3缺陷患者（C3D）中发现了一种血清因子，该因子可抑制C3溶血试验中所用缓冲液对照的溶血现象。由于缓冲液对照由EAC142、C5和C6 - 9试剂（C6 - 9R，通过用硫氰酸钾和水合肼处理豚鼠血清制备）组成，该因子似乎是一种不依赖C3的免疫溶血抑制剂。对C3D血清进行凝胶过滤和CM纤维素柱层析表明，该抑制剂可能是C8。在C8缺失的C3D血清中未观察到这种抑制作用。此外，发现分离出的C8以剂量依赖方式抑制C5和C6 - 9R对EAC142的溶血作用。因此，在该试验中发现C8是一种不依赖C3的免疫溶血抑制剂。进一步研究表明，C8还抑制C3、C5和C6 - 9R对EAC142的溶血作用（C3试验系统）或C5和C6 - 9R对EAC1423的溶血作用（C5试验系统），这表明样品中C8的存在可能会低估C3或C5的溶血活性。当使用人源的分离C6 - C9时，C8在试验系统中不抑制溶血，但当使用豚鼠源的分离C6 - C9代替C6 - 9R时，C8会抑制溶血。因此，提示人C8与豚鼠C6 - C9的不相容性可能是造成这种现象的原因。关于该机制的进一步实验清楚地表明，人C8通过在豚鼠C8之前与EAC1 - 7结合，抑制豚鼠C8和C9对EAC（带有人类C1 - C5以及豚鼠C6和C7的EA）的溶血作用。
