Human IgG and Streptococcus mutans SR protein contain cross-reactive epitopes.


Antigen B, a glycoprotein present on the cell surface of "mutans streptococci," mediates bacterial adherence to teeth surfaces and has been implicated in cross-reactivity with human heart components. Elevated levels of anti-IgG antibodies were generally found in sera of rabbits immunized with protein SR, a B-related protein from Streptococcus mutans serogroup f, or recombinant protein SR (rSR). These anti-IgG antibodies could be involved in the previously mentioned heart cross-reactivities. Results from immunoblots and ELISA analyses demonstrate that these anti-IgG antibodies recognize common epitopes on SR, rSR, and human IgG2 and IgG4 probably located on the Fab region. Furthermore, control experiments with biotinylated human IgG show that the cross-reactions between IgG and SR were not mediated by an FcR mechanism. Direct competition between rSR and human IgG in binding to anti-IgG or anti-SR antibodies confirm that S. mutans SR protein possesses Ag mimicry with human IgG. Our studies provide some evidence that S. mutans SR protein and human IgG H chains share autoimmune epitopes which could play a role in the induction of anti-IgG antibodies and therefore could explain the enhancement of anti-IgG antibody levels observed in rabbits immunized with either S. mutans whole cells or purified B-related Ag.

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@article{Wachsmann1989HumanIA, title={Human IgG and Streptococcus mutans SR protein contain cross-reactive epitopes.}, author={Dominique Wachsmann and F Ackermans and C. Vincenzotto and Monika Scholler and Herv{\'e} Bazin and Jo{\"{e}lle Ogier and J P Klein}, journal={Journal of immunology}, year={1989}, volume={143 12}, pages={4257-62} }