Opsonization of Cryptococcus neoformans by human immunoglobulin G: masking of immunoglobulin G by cryptococcal polysaccharide
Opsonization of Cryptococcus neoformans by human immunoglobulin G: masking of immunoglobulin G by cryptococcal polysaccharide
复制标题
人免疫球蛋白 G 对新型隐球菌的调理作用：隐球菌多糖掩蔽免疫球蛋白 G
作者：
T. McGaw;T. Kozel
以往的研究表明，未包裹的隐球菌与巨噬细胞的附着高度依赖于调理免疫球蛋白G(Ig G)，而隐球菌多糖抑制吞噬作用的附着阶段。我们研究了隐球菌多糖干扰免疫球蛋白调理作用的各种机制。隐球菌多糖不能显著阻止调理抗体与酵母的结合。此外，隐球菌多糖对免疫球蛋白的调理作用起到了非竞争性抑制作用。这些实验表明，细胞壁结合的免疫球蛋白以某种方式被掩盖，以至于它不能参与Fc介导的吞噬作用。情况似乎就是这样，因为隐球菌多糖抑制了抗血清对免疫球蛋白调理酵母细胞的凝集。抑制未包裹的新生隐球菌吞噬所需的多糖量与防止抗血清凝集IgG调理的隐球菌所需的多糖量之间存在良好的剂量-反应关系。如果将葡聚糖(一种已知可以增强几个颗粒凝集的物质)加入到介质中，则隐球菌多糖阻止抗血清凝集免疫球蛋白的隐球菌的能力丧失。
Previous studies have shown that attachment of non-encapsulated cryptococci to macrophages is highly dependent on opsonizing immunoglobulin G (IgG) and that cryptococcal polysaccharide inhibits the attachment phase of phagocytosis. We investigated various mechanisms by which cryptococcal polysaccharide might interfere with the opsonizing action of IgG. Cryptococcal polysaccharide did not appreciably prevent binding of opsonizing IgG to the yeast. Furthermore, cryptococcal polysaccharide acted as a noncompetitive inhibitor with respect to the opsonizing action of IgG. These experiments suggested that cell wall-bound IgG is masked in some manner such that it is unable to participate in Fc-mediated phagocytosis. This appeared to be the case, since cryptococcal polysaccharode inhibited agglutination of IgG-opsonized yeast cells by antiserum to IgG. There was good dose-response correlation between the amount of polysaccharide needed to inhibit phagocytosis of non-encapsulated Cryptococcus neoformans and the amount of polysaccharide needed to prevent agglutination of IgG-opsonized cryptococci by antiserum to IgG. The ability of cryptococcal polysaccharide to prevent agglutination of IgG-opsonized cryptococci by antiserum to IgG was lost if dextran, a substance known to enhance agglutination of several particles, was incorporated into the medium.