In vivo and in vitro reactions to antigens of Haemophilus influenzae in bronchial obstruction.

The frequency of precipitating antibody to heat-labile (H(1--2) and heat-stable (HCW and HCF) antigens of Haemophilus influenzae was determined in patients with asthma, chronic bronchitis, cystic fibrosis and bronchiectasis and compared with that in a control group. This showed that the immune response of asthmatic patients to heat-stable antigens was different from that to the heat-labile antigens. Exposure to antigens of H. influenzae is common in all the disease groups. Skin test reactions having the time course and macroscopic appearance of Type I (immediate) and Type III (late) were obtained after prick and intracutaneous skin testing with HCW antigen in varying concentrations in a group of patients with asthma, chronic bronchitis or cystic fibrosis and in a control group. It is suggested that IgE and short-term sensitizing IgG antibodies may be responsible for the immediate reactions while activation of the alternative pathway of complement by endotoxin contained in HCW could be responsible for the late reactions. HCW antigens were shown to release histamine from non-sensitized human leucocytes; HCW and HCF antigens were shown to release histamine from non-sensitized human lung. None of the antigens tested had an effect on beta-receptors in tracheal preparations. It is proposed that these reactions may contribute to the pathogenicity of H. influenzae in the lower respiratory tract.