Pangburn M K, Schreiber R D, Trombold J S, Müller-Eberhard H J
J Exp Med. 1983 Jun 1;157(6):1971-80. doi: 10.1084/jem.157.6.1971.
Erythrocytes from patients with paroxysmal nocturnal hemoglobinuria (PNH) contained a subpopulation that lacked membrane-associated Factor H-like activity present on normal human erythrocytes. Initial deposition of C3b on the erythrocytes was effected using a fluid phase C3 convertase. The cells were then treated with fluorescein-labeled C3 and the cell-bound C3 convertase. Analysis utilizing the fluorescence-activated cell sorter revealed two distinct cell populations, one of which was highly fluorescent, indicating a large number of C3b molecules per cell. Only this population (43%) was susceptible to lysis (44%) when exposed to acidified serum before C3b deposition. The less fluorescent population resembled normal human erythrocytes and was not affected by prior treatment with acidified serum. Since C3b deposition occurred almost exclusively on the complement-sensitive cells in the PNH erythrocyte population, these cells could be examined for the Factor H-like regulatory activities without prior isolation. These functions include enhancement of inactivation of erythrocyte-bound C3b by Factor I and acceleration of the decay of erythrocyte-bound C3 convertase, C3b,Bb. It was found that C3b on PNH erythrocytes was 100-fold less susceptible to inactivation by Factor I than C3b on normal human erythrocytes. The half-life at 22 degrees C of C3b,Bb on PNH erythrocytes was threefold greater than on normal human erythrocytes and similar to that of the enzyme bound to particles that do not possess Factor H-like activity. These observations suggest that the abnormal susceptibility of PNH erythrocytes to lysis by complement is due to a functional deficiency in one or more of the Factor H-like proteins present on normal human erythrocytes.
阵发性睡眠性血红蛋白尿（PNH）患者的红细胞含有一个亚群，该亚群缺乏正常人红细胞上存在的膜相关H因子样活性。使用液相C3转化酶使C3b初始沉积在红细胞上。然后用荧光素标记的C3和细胞结合的C3转化酶处理细胞。利用荧光激活细胞分选仪进行分析，发现了两个不同的细胞群体，其中一个群体具有高荧光性，表明每个细胞有大量的C3b分子。只有这个群体（43%）在C3b沉积前暴露于酸化血清时易被裂解（44%）。荧光性较低的群体类似于正常人红细胞，不受酸化血清预处理的影响。由于C3b沉积几乎只发生在PNH红细胞群体中对补体敏感的细胞上，因此无需事先分离即可检查这些细胞的H因子样调节活性。这些功能包括增强I因子对红细胞结合的C3b的灭活作用以及加速红细胞结合的C3转化酶C3b,Bb的衰变。研究发现，PNH红细胞上的C3b对I因子灭活的敏感性比正常人红细胞上的C3b低100倍。PNH红细胞上C3b,Bb在22℃的半衰期比正常人红细胞上的长三倍，与结合到不具有H因子样活性的颗粒上的酶的半衰期相似。这些观察结果表明，PNH红细胞对补体裂解的异常敏感性是由于正常人红细胞上存在的一种或多种H因子样蛋白的功能缺陷所致。
