Daha M R, Fearon D T, Austen K F
J Immunol. 1976 Jan;116(1):1-7.
C3 nephritic factor (C3NeF) defined by the capacity of nephritic serum and its fractions to initiate loss of the B antigen of C3 in normal serum was purified from the serum of three different donors and shown to function by stabilization of membrane-bound and fluid phase alternative pathway C3 convertase. C3NeF converts cell-bound C3B sites in a dose-related manner to CEB(NeF) sites, which exhibit an approximate 10-fold increase in half-life. The linear relationship between the C3NeF input and the residual hemolytic sites on EAC43B present after incubation for 20 min at 30 degrees C, during which labile C3B sites have decayed, indicates that the number of residual C3B sites is directly related to the dose of C3NeF. The capacity of C3NeF to stabilize the C3B convertase in a temperature- and dose-dependent manner, which is independent of binding or consumption of C3NeF, in a fluid phase reaction mixture of 125I-B, 131I-C3 and D permits isolation of a 10S complex containing radiolabeled C3 and B and exhibiting C3, convertase activity on an exogenous C3 source. Thus, the stabilizing effect of C3NeF is not limited to membrane-bound C3B but is also sufficient to permit recovery of a fluid phase C3 convertase formed during the interaction of C3, B, and D.
通过肾炎血清及其组分引发正常血清中C3的B抗原丢失的能力所定义的C3肾炎因子（C3NeF），从三名不同供体的血清中纯化得到，并显示其通过稳定膜结合和液相替代途径C3转化酶发挥作用。C3NeF以剂量相关的方式将细胞结合的C3B位点转化为CEB(NeF)位点，其半衰期增加约10倍。在30℃孵育20分钟后，不稳定的C3B位点已经衰变，此时C3NeF输入与EAC43B上残留溶血位点之间的线性关系表明，残留C3B位点的数量与C3NeF的剂量直接相关。在125I-B、131I-C3和D的液相反应混合物中，C3NeF以温度和剂量依赖的方式稳定C3B转化酶的能力，这与C3NeF的结合或消耗无关，允许分离出一种含有放射性标记C3和B的10S复合物，并对外源C3来源表现出C3转化酶活性。因此，C3NeF的稳定作用不仅限于膜结合的C3B，也足以使在C3、B和D相互作用过程中形成的液相C3转化酶得以恢复。
