Haemophilus influenzae release histamine and enhance histamine release from human bronchoalveolar cells. Examination of patients with chronic bronchitis and controls.

Haemophilus influenzae (H. influenzae), Streptococcus pneumoniae (S. pneumoniae) and Branhamella catarrhalis (B. catarrhalis) are often found in the lower respiratory tract of patients with chronic bronchitis. Earlier studies have shown that bacteria induce mediator release from human basophils and parenchymal lung mast cells. In this study the capability of bacteria to trigger or potentiate histamine release from superficially located mast cells in the airway epithelium was studied in cell suspensions obtained by bronchoalveolar lavage in patients with chronic bronchitis (CB). In approximately half of the patients H. influenzae and Staphylococcus aureus (S. aureus) were found to trigger histamine release, whereas no response was obtained by S. pneumoniae or B. catarrhalis. The mediator release was caused by a non-IgE-dependent mechanism. At lower concentrations of H. influenzae causing no histamine release the bacterium was found to enhance IgE-mediated histamine release triggered by anti-IgE antibody. The synergy was more pronounced in patients with CB than in controls. Since H. influenzae is found in the lower respiratory tract of the patients but not in normal individuals, the infection here may via histamine release lead to harmful effects on the airways of importance for precipitation and exacerbation of chronic bronchitis.