Comparative opsonic activity for Steptococcus mutans in oral fluids, and phagocytic activity of blood, crevicular, and salivary polymorphonuclear leucocytes in rhesus monkeys.

The opsonic activity for Streptococcus mutans was assayed in serum, gingival crevicular fluid, parotid saliva and mixed saliva from rhesus monkeys immunized against dental caries with a vaccine of Streptococcus mutans in Freund's incomplete adjuvant. The phagocytic activities of polymorphonuclear leucocytes from the blood and gingival crevice were compared, and the effects of gingival crevicular fluid and mixed saliva on blood polymorphonuclear leucocyte viability and phagocytic activity were assessed. Heat-stable opsonic activity was detected in sera, crevicular fluid, and mixed saliva of immunized animals. Polymorphonuclear leucocytes from the gingival crevice and saliva retained viability, although this was lower than in cells from blood. Exposure of blood polymorphonuclear leucocytes to crevicular fluid or mixed saliva for 30 min resulted in no loss of cell viability or phagocytic activity, but saliva was cytotoxic on prolonged exposure. These results support the hypothesis that the opsonization and phagocytosis of cariogenic bacteria might be a mechanism involved in the immunological protection against dental caries.