Coleman S E, Brady L J, Boyle M D
Department of Microbiology and Cell Science, University of Florida, College of Agriculture, Gainesville 32611-0116.
Infect Immun. 1990 Feb;58(2):332-40. doi: 10.1128/iai.58.2.332-340.1990.
We have characterized the immunoglobulin A (IgA)-Fc-binding properties and beta-antigen expression of several strains of group B streptococci by using ultrastructural immunocytochemistry. Colloidal gold-labeled tracers were used with intact and sectioned bacteria in order to gain information regarding the location and distribution of cell surface and cytoplasmic IgA-Fc-binding molecules and beta antigen. Colloidal gold (5- or 15-nm particles) was conjugated to IgA to characterize IgA-binding properties and to IgG to test for IgG binding. Rabbit anti-beta antiserum was reacted with the bacteria and then with protein G labeled with 15-nm colloidal gold particles. A double-labeling technique was used for simultaneous localization of IgA-Fc- and anti-beta-antibody-binding properties on sectioned bacteria. The data corroborated previous results which indicated that (i) IgA-Fc-binding and IgA-Fc-nonbinding forms of beta antigen can be secreted by strains which do not express beta antigen on the cell surfaces (HG806, VC75); (ii) differences in levels of expression of beta antigen and/or IgA-Fc-binding proteins can be detected among various group B isolates; (iii) group B streptococci do not express human IgG-Fc-binding proteins; and (iv) not all forms of beta antigen are capable of binding human IgA.
我们通过超微结构免疫细胞化学方法，对几株B族链球菌的免疫球蛋白A（IgA）-Fc结合特性和β抗原表达进行了表征。使用胶体金标记的示踪剂处理完整细菌和细菌切片，以获取有关细胞表面和细胞质IgA-Fc结合分子及β抗原的定位和分布信息。将胶体金（5纳米或15纳米颗粒）与IgA偶联以表征IgA结合特性，与IgG偶联以检测IgG结合情况。兔抗β抗血清与细菌反应，然后与用15纳米胶体金颗粒标记的蛋白G反应。采用双重标记技术同时定位细菌切片上的IgA-Fc结合特性和抗β抗体结合特性。这些数据证实了先前的结果，即：（i）细胞表面不表达β抗原的菌株（HG806、VC75）能够分泌β抗原的IgA-Fc结合和IgA-Fc非结合形式；（ii）在不同的B族分离株中可检测到β抗原和/或IgA-Fc结合蛋白表达水平的差异；（iii）B族链球菌不表达人IgG-Fc结合蛋白；（iv）并非所有形式的β抗原都能与人IgA结合。
