Morgan B P, Dankert J R, Esser A F
J Immunol. 1987 Jan 1;138(1):246-53.
Nucleated cells can resist lysis by and recover from complement attack even after formation of the potentially cytolytic membrane attack complex on the cell surface. We have found that human neutrophils resist complement lysis by the physical removal of membrane attack complexes by both endocytic and exocytic process. The latter mechanism predominates, vesiculation being detectable within 60 sec of initiating the complement cascade. Sixty-five percent of the formed complexes are removed on plasma membrane vesicles, although only 2% of the cell surface is lost. Ultrastructural examination revealed that these vesicles were covered with ring-like "classical" complement lesions. Analysis of these vesicles by gel electrophoresis indicated that C9 was present exclusively in the form of a sodium dodecyl sulfate-resistant, high m.w. complex. In contrast, the 35% of C9 that remained associated with the cells was found to be inaccessible to a C9-specific monoclonal antibody, and was partly degraded, suggesting internalization of the membrane attack complex and proteolysis of some C9 molecules. The molar ratio of C9 to C8 was 12 to 1 on shed vesicles and on recovered cells.
有核细胞即使在细胞表面形成潜在的溶细胞性膜攻击复合物后，仍能抵抗补体攻击并从中恢复。我们发现，人类中性粒细胞通过内吞和外排过程物理性地去除膜攻击复合物来抵抗补体裂解。后一种机制占主导，在启动补体级联反应后60秒内即可检测到囊泡形成。尽管仅损失2%的细胞表面，但65%形成的复合物在质膜囊泡上被清除。超微结构检查显示，这些囊泡覆盖着环状的“经典”补体损伤。通过凝胶电泳对这些囊泡进行分析表明，C9仅以耐十二烷基硫酸钠的高分子量复合物形式存在。相比之下，发现仍与细胞相关的35%的C9无法被C9特异性单克隆抗体识别，并且部分降解，这表明膜攻击复合物发生了内化以及一些C9分子发生了蛋白水解。脱落的囊泡和恢复后的细胞上C9与C8的摩尔比为12比1。
