Humoral immune response to mutans streptococci associated with dental caries

Mutans streptococci are important aetiological agents in dental caries and their prolonged contact with oral tissues evokes a variety of immune responses through local secretory and systemic antibodies. Patterns of such humoral responses in Indian children have not been reported and we undertook the present study to examine these.

One hundred and twenty-six children with dental caries and 55 matched controls were studied and saliva and sera collected from them. The tests on these specimens included total salivary and systemic immunoglobulins of different classes using radial immunodiffusion and Streptococcus mutans specific IgA, IgG and IgM using specifically standardized enzyme immunoassays.

Children with caries had higher levels of IgG (1350 +/- 9.9 mg/dl; controls 1110 +/- 6.7 mg/dl) and IgA (260 +/- 1.8 mg/dl; controls 190 +/- 1 mg/dl) in the serum but their saliva had lower levels of total IgG (160 +/- 0.7 mg/dl; controls 340 +/- 2.9 mg/dl) and IgA (130 +/- 0.5 mg/dl; controls 410 +/- 3 mg/dl). IgM levels in caries children and controls were not significantly different. Higher levels of Streptococcus mutans specific IgA were detected in the saliva of 95 out of 126 (75%) children with caries compared to 13 out of 55 (22%) controls. Specific serum IgG and IgA levels were also increased in 105 and 114 children with caries, although the levels were not as high as those in saliva. Total and specific salivary and serum IgM antibodies were similar in children with caries and control subjects.

The nature of the humoral immune response in Indian children with dental caries suggests that Streptococcus mutans specific salivary and serum antibodies may play a major role in pathogenesis. Our findings may have importance when devising methods for follow up and prognosis as well as for vaccination strategies.