Inhibition of adhesion of Haemophilus influenzae to buccal cells by respiratory secretions.

The ability of salivary secretions and sputum sol from patients with chronic bronchitis to inhibit the adhesion of non-serotypable Haemophilus influenzae to human buccal epithelial cells has been examined. Specific H. influenzae antibodies were measured by an enzyme-linked immunosorbent assay (ELISA). Saliva and sputum levels of anti-H. influenzae immunoglobulin A (IgA) antibody were related inversely to buccal cell adherence (r = -0.92). Absorption of saliva and sputum sol with H. influenzae removed antibody detected by ELISA but only partially removed inhibition of attachment of bacteria. In patients with a history of recurrent bronchitis significantly more inhibitory activity remained after absorption of the secretory IgA (sIgA) specific antibody compared with patients who were resistant to acute episodes of infection (P less than 0.05). These observations suggest that factors, other than sIgA, are present in respiratory secretions and are capable of modulating H. influenzae attachment to buccal epithelial cells.