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.
Wachsmann
D
D
National Institute of Health and Medical Research U157, Faculty of Dentistry, Strasbourg, France.
Ackermans
F
F
Vincenzotto
C
C
Scholler
M
M
Bazin
H
H
Ogier
J
J
Klein
J P
JP
D000818:Animals; D000907:Antibodies, Bacterial / Q000032:analysis; D000942:Antigens, Bacterial / Q000276:immunology*; D001426:Bacterial Proteins / Q000276:immunology*; D001666:Binding Sites, Antibody; D003429:Cross Reactions; D000939:Epitopes / Q000276:immunology*; D006801:Humans; D007074:Immunoglobulin G / Q000378:metabolism*; D009206:Myocardium / Q000276:immunology; D011817:Rabbits; D013295:Streptococcus mutans / Q000276:immunology*
D000907:Antibodies, Bacterial; D000942:Antigens, Bacterial; D001426:Bacterial Proteins; D000939:Epitopes; D007074:Immunoglobulin G