Noel G J, Katz S L, Edelson P J
Department of Pediatrics, Cornell University Medical College, New York, New York 10021.
Pediatr Res. 1991 Jul;30(1):118-23. doi: 10.1203/00006450-199107000-00023.
To understand how complement effects phagocytosis of type III group B streptococcus, we assessed the specific role of C3 in mediating binding and ingestion of these bacteria by macrophages. Phagocytosis of bacteria by resident mouse peritoneal macrophages was measured under conditions in which C3 deposition on bacteria was inhibited or after blockade of C3-ligands or of complement receptor type three (CR3) with specific antibodies. C3 depletion, incubation with F(ab')2 fragments of antibody to C3, or blockade of CR3 completely inhibited the binding of bacteria that was seen in the presence of nonimmune serum. Immune serum increased the number of associated organisms 6-fold compared to that seen with nonimmune serum. With this serum, 82% of organisms were ingested. C3 depletion or CR3 blockage had a modest effect, but this interaction could be ablated completely only after Fc receptors were blocked. Using varied concentrations of an IgG2a MAb against type III capsular antigen, it was possible to show that small amounts of antibody incapable of mediating bacterial binding by itself directed an interaction that also depended upon C3. Phagocytosis of group B streptococci by macrophages in the presence of little or no antibody requires complement and C3 opsonization specifically. C3-dependent binding may be important in determining mononuclear phagocyte-dependent clearance of these pathogens from blood, particularly in patients with little or no type-specific serum antibody.
为了解补体如何影响B族链球菌III型的吞噬作用，我们评估了C3在介导巨噬细胞对这些细菌的结合和摄取中的特定作用。在抑制细菌上C3沉积的条件下，或在用特异性抗体阻断C3配体或补体受体3型（CR3）后，测量常驻小鼠腹膜巨噬细胞对细菌的吞噬作用。C3耗竭、与抗C3抗体的F(ab')2片段孵育或阻断CR3，均可完全抑制在非免疫血清存在下观察到的细菌结合。与非免疫血清相比，免疫血清使相关生物体的数量增加了6倍。使用这种血清时，82%的生物体被摄取。C3耗竭或CR3阻断有一定作用，但只有在Fc受体被阻断后，这种相互作用才能被完全消除。使用不同浓度的抗III型荚膜抗原的IgG2a单克隆抗体，有可能表明少量自身无法介导细菌结合的抗体可引导一种也依赖于C3的相互作用。在几乎没有或没有抗体的情况下，巨噬细胞对B族链球菌的吞噬作用特别需要补体和C3调理作用。C3依赖性结合可能在决定单核吞噬细胞对这些病原体的血液清除中起重要作用，特别是在几乎没有或没有型特异性血清抗体的患者中。
