Amount and avidity of salivary and serum antibodies against Streptococcus mutans in two groups of human subjects with different dental caries susceptibility.

Immunoglobulin A (IgA) and IgG antibodies against Streptococcus mutans K1R and 10449 were measured in serum and in stimulated whole saliva from two groups of naval recruits, representing high or low caries susceptibility. The antibody assays were performed by using the enzyme-linked immunosorbent assay, and the results were expressed by a method able to estimate the amount of high-avidity and total specific antibodies. As a control, concentrations of salivary total immunoglobulins were related to the amounts of specific antibodies. Further, antibodies were assayed against three antigens, unrelated to the streptococci. No clear differences were observed in serum antibodies between the subjects with high or low caries susceptibility. However, in saliva, low caries susceptibility was associated with a high amount of total antigen-specific IgA, and possibly IgG, against S. mutans. This difference between the groups still existed when the amounts of specific antibodies were related to the amounts of salivary immunoglobulins. There were no differences in the amounts of total specific antibodies against the unrelated antigens. No differences were observed in the estimates of high-avidity anti-S. mutans antibodies between the groups, either in serum or saliva. Thus, within the limitations of the assays and crude antigen, lack of high-avidity antibodies is not responsible for caries susceptibility. Instead, the amount of anti-S. mutans antibodies seems to be linked with caries protection. The results of the present study indicate that salivary antibodies are linked with the control of human dental caries.