King B F, Wilkinson B J
Infect Immun. 1981 Sep;33(3):666-72. doi: 10.1128/iai.33.3.666-672.1981.
Recent studies of the mechanism of resistance to phagocytosis in encapsulated Staphylococcus aureus have suggested that the capsule is readily penetrated by high-molecular-weight proteins such as antibodies and complement components. S. aureus strains contain a cell wall protein, protein A, that reacts with the Fc portion of immunoglobulins. The binding of immunoglobulin G (IgG) to encapsulated and unencapsulated S. aureus strains has been studied to assess the penetrability of the S. aureus capsule by IgG. Encapsulated S. aureus strains M and Smith diffuse bound large amounts of human IgG which were comparable to amounts bound by the unencapsulated strains Cowan I, M variant, and Smith compact. Trypsin treatment of bacteria reduced their ability to bind IgG. Bound IgG was not removed by extensive washing of bacteria with buffer. A non-protein A-containing, coagulase-negative, encapsulated staphylococcal strain did not bind IgG. These observations suggest that IgG is binding to cell wall protein A in encapsulated S. aureus. No differences in the rates of IgG binding by encapsulated and unencapsulated S. aureus strains were observed. It is concluded that the S. aureus capsule is freely permeable to IgG. This is of importance in considerations of the mechanisms of resistance to phagocytosis and antigen masking in encapsulated microorganisms.
近期对包膜金黄色葡萄球菌抗吞噬作用机制的研究表明，该菌的荚膜很容易被抗体和补体成分等高分子量蛋白质穿透。金黄色葡萄球菌菌株含有一种细胞壁蛋白A，它能与免疫球蛋白的Fc部分发生反应。为了评估IgG对金黄色葡萄球菌荚膜的穿透性，研究人员对包膜和未包膜的金黄色葡萄球菌菌株与免疫球蛋白G（IgG）的结合情况进行了研究。包膜金黄色葡萄球菌菌株M和史密斯菌株能大量扩散结合人IgG，其结合量与未包膜的考恩I菌株、M变异株和史密斯致密株相当。用胰蛋白酶处理细菌会降低它们结合IgG的能力。通过用缓冲液大量洗涤细菌，无法去除结合的IgG。一株不含蛋白A、凝固酶阴性的包膜葡萄球菌菌株不结合IgG。这些观察结果表明，IgG在包膜金黄色葡萄球菌中与细胞壁蛋白A结合。未观察到包膜和未包膜金黄色葡萄球菌菌株结合IgG的速率存在差异。由此得出结论，金黄色葡萄球菌的荚膜对IgG是自由通透的。这对于考虑包膜微生物的抗吞噬作用机制和抗原掩盖具有重要意义。
