Changing agglutination activities of salivary immunoglobulin A preparations against oral streptococci

Immunoglobulin A (IgA) was prepared from samples of parotid saliva collected from two individuals over a 150-day period. Standardized solutions of the IgA were tested for agglutinating antibody activity against strains of streptococcus salivarius, S. sanguis, S. mitis, and S. mutans that had been isolated from a homologous individual on day 30 and preserved in the lyophilized state. The agglutinating activity of the standardized IgA preparations against these strains was found to change over time, whereas the agglutination patterns of IgA prepared from saliva samples collected 3 days apart were generally similar. Differences in agglutination titers were also observed between IgA samples prepared from saliva collected on day 0 and day 150. The data indicate that the oral cavity may harbor streptococci of different antigenic composition representing the same species at a given time and that parotid IgA agglutinating antibody against these serotypes changes over time.