Akagaki Y, Inai S
Mol Immunol. 1983 Nov;20(11):1221-6. doi: 10.1016/0161-5890(83)90146-3.
The complement fixing ability of the F(ab')2 fragment of human IgG was studied using an immune precipitate (Ippt) formed between tetanus toxoid and the F(ab')2 of high-titer IgG antibody against tetanus toxin. A major subclass of the specific IgG antibody against tetanus toxin, which was separated by affinity column chromatography, was identified as IgG1. On incubation of normal human serum (NHS) with the Ippt formed at equivalence, a dose-dependent consumption of CH50, C3 and C5 activities was observed without significant loss of the early acting complement components. A similar consumption of CH50, C3 and C5 activities was found in NHS reacted with Ippt formed at any antigen/antibody ratio. The Ippt formed at antibody excess was more efficient in complement consumption than the Ippt formed at antigen excess. An apparent consumption of C3 and C5 activities was also noted in C4-deficient guinea pig serum treated with Ippt. When Ippt was incubated with Mg2+--EGTA-treated NHS, both C3 and C5 convertases of the alternative pathway were generated on the Ippt. From these results, it was concluded the the F(ab')2 of human IgG antibody, especially IgG1 antibody, when it formed an Ippt with antigen, could activate the alternative complement pathway.
利用破伤风类毒素与抗破伤风毒素的高效价IgG抗体的F(ab')2片段形成的免疫沉淀物（Ippt），研究了人IgG的F(ab')2片段的补体固定能力。通过亲和柱层析分离出的抗破伤风毒素特异性IgG抗体的一个主要亚类被鉴定为IgG1。当正常人血清（NHS）与等当量形成的Ippt孵育时，观察到CH50、C3和C5活性呈剂量依赖性消耗，早期作用的补体成分无明显损失。在与任何抗原/抗体比例形成的Ippt反应的NHS中也发现了类似的CH50、C3和C5活性消耗。抗体过量时形成的Ippt比抗原过量时形成的Ippt在补体消耗方面更有效。在用Ippt处理的C4缺陷豚鼠血清中也观察到C3和C5活性的明显消耗。当Ippt与Mg2+ - EGTA处理的NHS孵育时，在Ippt上产生了替代途径的C3和C5转化酶。从这些结果得出结论，人IgG抗体的F(ab')2片段，尤其是IgG1抗体，当其与抗原形成Ippt时，可激活替代补体途径。
