Levy N J, Kasper D L
J Immunol. 1986 Jun 1;136(11):4157-62.
The role of surface-bound type Ia group B Streptococcus (GBS) capsular polysaccharide in antibody-independent binding of C1 and activation of the classic complement pathway was investigated. In a radiolabeled bacterial-polymorphonuclear leukocyte (PMN) association assay, a measure of bacterial opsonization, preincubation of 3H-type Ia GBS with purified F(ab')2 to the organism blocked the association of the bacteria with PMN', and the inhibitory effect was dose dependent. The specificity of F(ab')2 blocking was shown after adsorption of F(ab')2 with type Ia polysaccharide-sensitized erythrocytes. Polysaccharide-adsorbed F(ab')2 had a 70% decrease in ability to block the association of bacteria with PMN. Evidence for the requirement of the capsular polysaccharide in classic complement pathway activation came from a C1 transfer assay with the use of neuraminidase-digested type Ia GBS. Neuraminidase digestion removed 80% of the terminal sialic acid residues from the native polysaccharide. These neuraminidase-digested organisms had a 72% decrease in binding and transfer of purified C1 compared with non-enzyme-treated organisms. Type Ia capsular polysaccharide bound to sheep erythrocytes promoted classic complement pathway-mediated hemolysis of the cells. The role of C1 inhibitor (INH) in modulation of C1 activation by the organisms was investigated. The possibility existed that the C1 INH could be bound by the bacteria, allowing C1 activation to occur in the fluid phase. The inhibitor was purified from human serum, and its activity was measured before and after incubation with type Ia GBS. The organisms had no effect on C1 INH activity. Thus surface-bound capsular polysaccharide of type Ia GBS mediates C1 binding and classic pathway activation, and this does not involve the C1 INH.
研究了表面结合的Ia型B族链球菌（GBS）荚膜多糖在C1的非抗体依赖性结合及经典补体途径激活中的作用。在放射性标记的细菌-多形核白细胞（PMN）结合试验（一种衡量细菌调理作用的方法）中，用针对该菌的纯化F(ab')2预孵育3H-Ia型GBS可阻断细菌与PMN的结合，且抑制作用呈剂量依赖性。在用Ia型多糖致敏红细胞吸附F(ab')2后，显示了F(ab')2阻断的特异性。经多糖吸附的F(ab')2阻断细菌与PMN结合的能力下降了70%。经典补体途径激活中对荚膜多糖需求的证据来自使用神经氨酸酶消化的Ia型GBS进行的C1转移试验。神经氨酸酶消化去除了天然多糖中80%的末端唾液酸残基。与未用酶处理的细菌相比，这些经神经氨酸酶消化的细菌在纯化C1的结合和转移方面下降了72%。与绵羊红细胞结合的Ia型荚膜多糖促进了细胞的经典补体途径介导的溶血。研究了C1抑制剂（INH）在调节细菌对C1激活中的作用。存在C1 INH可能被细菌结合从而使C1在液相中发生激活的可能性。该抑制剂从人血清中纯化得到，并在与Ia型GBS孵育前后测量其活性。这些细菌对C1 INH活性没有影响。因此，Ia型GBS的表面结合荚膜多糖介导C1结合和经典途径激活，且这一过程不涉及C1 INH。
