Tyler B M, Cole M F
Department of Microbiology and Immunology, Georgetown University Medical Center, Washington, DC 20007, USA.
Microbiol Immunol. 1998;42(7):503-8. doi: 10.1111/j.1348-0421.1998.tb02316.x.
Secretory IgA (SIgA) is the principal immunoglobulin isotype present in the mucosal secretions of humans. SIgA is thought to play a major role in host defense at these surfaces by inhibiting the colonization of potentially pathogenic microorganisms. A number of bacteria that are mucosal pathogens of humans produce a protease that specifically cleaves the IgA1 subclass of humans and great apes at the hinge region to produce Fab and Fc fragments. In order to study the effect of IgA1 protease on the ability of SIgA1 antibodies to inhibit bacterial adherence, an in vitro assay that quantifies the adsorption of radiolabeled Streptococcus mutans to hydroxyapatite (HA) beads was employed. High titer S. mutans-specific SIgA1 and SIgA2 antibodies were induced in chimpanzee milk for use in the assay. Fab alpha1 fragments had significantly reduced ability to inhibit adherence of S. mutans to saliva-coated HA compared to intact SIgA1 or SIgA2 anti-S. mutans antibodies. These data support the potential importance of IgA1 proteases as an ecological determinant in the oral cavity and their role as a determinant of pathogenesis of pathogenic bacteria whose portal of entry is the mucosal surface.
分泌型IgA（SIgA）是人类黏膜分泌物中主要的免疫球蛋白同种型。SIgA被认为通过抑制潜在致病微生物的定植在这些表面的宿主防御中发挥主要作用。许多作为人类黏膜病原体的细菌会产生一种蛋白酶，该蛋白酶能在铰链区特异性切割人类和大猩猩的IgA1亚类，产生Fab和Fc片段。为了研究IgA1蛋白酶对SIgA1抗体抑制细菌黏附能力的影响，采用了一种体外测定法，该方法可定量放射性标记的变形链球菌对羟基磷灰石（HA）珠的吸附。在黑猩猩乳汁中诱导产生高滴度的变形链球菌特异性SIgA1和SIgA2抗体用于该测定。与完整的SIgA1或SIgA2抗变形链球菌抗体相比，Fab α1片段抑制变形链球菌黏附于唾液包被的HA的能力显著降低。这些数据支持了IgA1蛋白酶作为口腔生态决定因素的潜在重要性及其作为致病细菌发病机制决定因素的作用，这些致病细菌的进入门户是黏膜表面。
