Natural antibodies in man to a protein antigen from the bacterium Streptococcus mutans related to dental caries experience.

Serum antibodies to a cell-wall protein antigen derived from Streptococcus mutans (SA I/II) were examined in 108 subjects by a solid-phase radioimmunoassay. As a control, antibodies to lipoteichoic acid and to Strep. mutans whole cells were examined and the relationship to dental caries of isotype-specific antibodies to both antigens determined. Serum-IgG antibodies to SA I/II and to Strep. mutans were significantly greater in subjects of low caries experience than in subjects of high caries experience, whereas serum-IgG antibodies to LTA showed no relationship. Serum-IgM antibodies to SA I/II were depressed in subjects with carious lesions, whereas IgM antibodies to Strep. mutans in the same subjects were raised. IgA antibodies against any antigen were not related to caries. Serum antibodies of each isotype to SA I/II were generally positively-correlated with antibodies to LTA but inhibition experiments demonstrated specificity of antibodies for each antigen. The relationship between antibodies to SA I/II and dental caries are consistent with those reported with antibodies to whole cells of Strep. mutans and suggest that high-serum IgG antibodies to SA I/II may be associated with protection against dental caries in man.