Densen P, McRill C M, Ross S C
Department of Medicine, Veterans Administration Medical Center, Iowa City.
J Immunol. 1988 Dec 1;141(11):3902-9.
C3, C4, factor B, properdin, and C2 binding to serum-sensitive and serum-resistant gonococci was quantitated in C8-deficient and normal human serum by using fluorescein-conjugated antibodies and 3H-labeled components. Organism and serum-specific differences were noted, the most striking of which involved factor B and properdin binding to the serum-sensitive strains in the different sera. C3 binding to these organisms was quantitatively and kinetically equivalent in C8-deficient and normal human serum. In contrast, factor B and properdin binding reached a plateau after 5 min in C8-deficient serum but peaked and fell to control values in normal human serum. Identical results were obtained with normal human serum immunochemically depleted of C8. Between 7 and 15% of the bound C3 participated in formation of the alternative pathway convertase C3bBb/P. Reconstitution of the C cascade by adding purified C8 to C8-deficient serum led to the loss of factor B previously bound to the organisms. Factor B loss occurred coincident with bacterial killing and membrane disruption as observed by electron microscopy. Prevention of membrane disruption by depleting normal human serum of lysozyme had no effect on killing and failed to prevent factor B loss. Stabilization of the C3bBb complex with Ni2+ prevented factor B loss as well as gross membrane disruption but not bacterial killing. C2 (the classical pathway analog of factor B) binding to gonococci was equivalent in C8-deficient and normal human serum peaking within 2.5 min and falling to control values in both sera thereafter. We conclude that the assembly of the membrane attack complex promotes decay of C3bBb/P with release of factor B and properdin but not C3 from the organism surface. Membrane disruption does not appear to be required for this effect. This activity may represent a mechanism to limit continued C consumption.
通过使用荧光素偶联抗体和³H标记成分，对C8缺陷型和正常人血清中C3、C4、B因子、备解素和C2与血清敏感型和血清抗性淋球菌的结合进行了定量分析。观察到了菌株和血清特异性差异，其中最显著的差异涉及不同血清中B因子和备解素与血清敏感型菌株的结合。在C8缺陷型和正常人血清中，C3与这些菌株的结合在数量和动力学上是相当的。相比之下，在C8缺陷型血清中，B因子和备解素的结合在5分钟后达到平台期，而在正常人血清中则先达到峰值然后降至对照值。用免疫化学方法去除C8的正常人血清也得到了相同的结果。7%至15%的结合C3参与了替代途径转化酶C3bBb/P的形成。向C8缺陷型血清中添加纯化的C8来重建补体级联反应，导致先前结合在菌株上的B因子丢失。B因子的丢失与电子显微镜观察到的细菌杀伤和膜破坏同时发生。通过去除正常人血清中的溶菌酶来防止膜破坏，对杀伤作用没有影响，也不能阻止B因子的丢失。用Ni²⁺稳定C3bBb复合物可防止B因子丢失以及严重的膜破坏，但不能阻止细菌杀伤。C2（B因子的经典途径类似物）与淋球菌的结合在C8缺陷型和正常人血清中相当，在2.5分钟内达到峰值，此后在两种血清中均降至对照值。我们得出结论，膜攻击复合物的组装促进了C3bBb/P的衰变，导致B因子和备解素从生物体表面释放，但不会导致C3释放。这种效应似乎不需要膜破坏。这种活性可能代表了一种限制补体持续消耗的机制。
