Swanson J, Hsu K C, Gotschlich E C
J Exp Med. 1969 Nov 1;130(5):1063-91. doi: 10.1084/jem.130.5.1063.
The presence of M antigens on group A streptococci is associated with hairlike fimbriae that cover the surface of the streptococcal cell wall and are demonstrable by electron microscopy. These fimbriae also may be associated with R antigen. Like M protein, the surface fimbriae are destroyed by trypsin treatment and reappear when "trypsinized" streptococci are reincubated in fresh, trypsin-free broth. Ferritin-conjugated, type-specific antibodies localize on homologous M+ cells in a pattern suggestive of several M antigenic sites along the length of individual surface fimbria. The M-associated fimbriae remain on the residual cell wall after removal of the bulk of group-specific polysaccharide through nitrous acid extraction. This suggests attachment of the fimbriae to the mucopeptide and minor polysaccharide components remaining in the nitrous acid-extracted wall. The pattern of localization of ferritin-conjugated antibodies on homologous streptococci before and after trypsin exposure and upon reincubation of the trypsinized cells in fresh medium suggests the following hypothesis: M antigen is secreted by the cell, is partially excreted through the otherwise intact cell wall, and is bound by the wall so that M protein occupies a peripheral, exposed position on the surfaces of the streptococcal cell wall.
A 群链球菌上 M 抗原的存在与覆盖在链球菌细胞壁表面的毛发状菌毛有关，通过电子显微镜可观察到这些菌毛。这些菌毛也可能与 R 抗原有关。与 M 蛋白一样，表面菌毛经胰蛋白酶处理后会被破坏，而当“经胰蛋白酶处理的”链球菌在新鲜的、不含胰蛋白酶的肉汤中再次培养时，菌毛又会重新出现。铁蛋白结合的型特异性抗体以一种模式定位于同源 M+细胞上，提示沿着单个表面菌毛的长度存在几个 M 抗原位点。通过亚硝酸提取去除大部分群特异性多糖后，与 M 相关的菌毛仍保留在残留的细胞壁上。这表明菌毛附着于亚硝酸提取的细胞壁中残留的粘肽和少量多糖成分上。在胰蛋白酶处理前后以及经胰蛋白酶处理的细胞在新鲜培养基中再次培养时，铁蛋白结合抗体在同源链球菌上的定位模式提示了以下假说：M 抗原由细胞分泌，部分通过原本完整的细胞壁排出，并与细胞壁结合，使得 M 蛋白占据链球菌细胞壁表面的外周暴露位置。
