Inhibition of bacterial adherence by nasopharyngeal secretions.

The role of secretory immunoglobulin (Ig) A in nasopharyngeal secretions in the adherence of Streptococcus pneumoniae and Hemophilus influenzae to nasopharyngeal epithelial cells was investigated in vitro. The adherence was remarkably reduced by treating bacteria with nasopharyngeal secretions, and the antiadhesive activity was significantly greater in nasopharyngeal secretions having secretory IgA antibody activity against bacteria than in those having no activity. Noticeable changes were not observed in the antiadhesive activity caused by absorption of IgG from nasopharyngeal secretions. Results suggest that secretory IgA in nasopharyngeal secretions is related to bacterial adherence and adds to the prevention of nasopharyngeal infections.