Effective Immunity to Dental Caries: Studies of Active and Passive Immunity to Streptococcus mutans in Malnourished Rats

Abstract

The present studies suggest that rat dams passively transfer IgG to their offspring via milk. Furthermore, rat dams hyperimmunized to S mutans after intravenous administration of this bacterium have serum-precipitating antibody to S mutans group-specific antigen. This serum precipitin was also observed in serums of their offspring during the suckling period and was detectable for a week after weaning. When these offspring were infected with S mutans on the day of weaning, significantly fewer smooth surface lesions developed in them than in infected rats reared on nonimmunized mothers. These results suggest that anti-S mutans antibody, perhaps of the IgG2a class, is passively transferred from mother to offspring via the milk. Furthermore, this antibody is probably important in protection against S mutans infection. In this regard, recent studies by Lehner, Challacombe, and Caldwell have suggested that crevicular fluid transudating serum antibodies are important in the prevention of dental caries in rhesus monkeys. From our studies and others, it is becoming clear that at least two sources and classes of antibody are important in caries immunity. Secretory IgA, produced and secreted into saliva after local injection can be correlated with protection. At the same time, serum antibody (presumably IgG) either passively or actively derived also gives immune protection. Further studies must clarify the precise role of these Ig's and their possible synergistic activity with other specific immune factors in saliva in order to determine the mechanism(s) involved in effective caries immunity.