Secretory IgA adsorption and oral streptococcal adhesion to human enamel and artificial solid substrata with various surface free energies.

In this paper, secretory IgA adsorption from a single component sIgA solution and from human whole saliva onto human enamel and artificial solid substrata with various surface free energies was studied as a function of time. ELISA indicated that screening or displacement of adsorbed sIgA by other salivary proteins occurred only on low surface free energy substrata, not on high surface free energy substrata such as enamel. In addition, the adhesion of three oral streptococcal strains (Streptococcus mitis BMS, S. sanguis 12, and S. mutans NS), also having widely different surface free energies, to sIgA-coated surfaces was studied. The adhesion of all three streptococcal strains was significantly reduced in the presence of a sIgA coating. However, ranking the adhesion data with respect to the various substrata revealed a similar order to that in the case of uncoated substrata, indicating that substratum properties were at least partly transferred by the adsorbed protein film to the interface with adhering micro-organisms. For S. sanguis 12 and S. mitis BMS, adhesion decreased proportionally with the amounts of sIgA detected by ELISA, but for S. mutans NS such relations with the amounts of sIgA detected on the protein-coated substrata were not found. Thus, for S. mutans NS a specific antibody effect seems to exist in addition to a non-specific protein effect like that observed for S. sanguis 12 and S. mitis BMS.