Myhre E B, Kronvall G
Infect Immun. 1980 Mar;27(3):808-16. doi: 10.1128/iai.27.3.808-816.1980.
Forty-seven bacterial strains representing four different group C streptococcal species were tested for binding of human and bovine immunoglobulin G (IgG) subclasses. Specific binding sites for IgG were found in all bacterial species studied. The four species included differed, however, in their capacities to interact with various IgG subclasses, indicating the existence of different types of IgG receptors. Streptococcus equisimilis and Streptococcus dysgalactiae were found to carry the same type of IgG receptor, one that is identical to the previously described Fc-binding structure type III. A new type of bacterial IgG receptor was detected in Streptococcus zooepidemicus strains. This receptor exhibits a protein A-like subclass specificity, with binding of human IgG1, IgG2, and IgG4 and of bovine IgG2. However, differences in their capacities to interact with other non-human immunoglobulins indicated that these two immunoglobulin-reactive structures were different. All types of IgG receptors in group C streptococci were found to be heat stable but susceptible to proteolytic enzymes. The inability of human serum albumin or fibrinogen to inhibit the uptake of radiolabeled IgG shows that the IgG receptor is separate from binding sites for these two other proteins on the bacterial cell surface. The existence of similar IgG receptors in closely related streptococcal species suggests that these structures have a common origin.
对代表四种不同C组链球菌的47株细菌进行了人及牛免疫球蛋白G（IgG）亚类结合试验。在所研究的所有细菌种类中均发现了IgG的特异性结合位点。然而，所包含的这四种细菌在与各种IgG亚类相互作用的能力方面存在差异，这表明存在不同类型的IgG受体。发现马链球菌和停乳链球菌携带相同类型的IgG受体，即与先前描述的III型Fc结合结构相同的受体。在兽疫链球菌菌株中检测到一种新型的细菌IgG受体。该受体表现出类蛋白A的亚类特异性，可与人IgG1、IgG2和IgG4以及牛IgG2结合。然而，它们与其他非人类免疫球蛋白相互作用能力的差异表明这两种免疫球蛋白反应结构是不同的。发现C组链球菌中的所有类型的IgG受体均对热稳定，但易受蛋白水解酶的影响。人血清白蛋白或纤维蛋白原无法抑制放射性标记IgG的摄取，这表明IgG受体与细菌细胞表面上这两种其他蛋白质的结合位点是分开的。密切相关的链球菌种类中存在相似的IgG受体，这表明这些结构有共同的起源。
