Airway hyperresponsiveness to non-specific stimuli is one characteristic feature of airway diseases such as bronchial asthma and chronic bronchitis. Until now, studies aiming to demonstrate a relationship between in vivo conditions associated with airway hyperreactivity and in vitro airway responsiveness have been inconclusive.
Since serum immunoglobulin (Ig) E is believed to be one determinant of airway reactivity in vivo, we studied whether in vitro airway reactivity in lung resection material from patients with elevated levels of serum IgE was increased as compared with patients with undetectable IgE. By this approach, we aimed to elucidate the role of circulating IgE for bronchial smooth muscle reactivity in vitro.
Bronchial rings from nine patients with total serum IgE levels above 200 U/mL and 10 patients with total serum IgE levels below 10 U/mL were passively sensitized, i.e. incubated overnight with buffer or sensitizing serum containing high levels of total IgE (> 250 U/mL). Afterwards, contractile responses to histamine were assessed in the organ bath.
Histamine responsiveness was significantly increased in airways obtained from patients with IgE levels above 200 U/mL as compared with airways from patients with IgE levels below 10 U/mL (P < 0.05). Passive sensitization of bronchi from patients with low IgE significantly increased histamine responsiveness, as compared with non-sensitized controls from the same patients (P < 0.05). In contrast, passive sensitization of airways from patients with elevated IgE did not further increase responsiveness. There was no difference in histamine reactivity between non-passively sensitized and passively sensitized tissue preparations from patients with IgE above 200 U/mL and passively sensitized tissues from patients with IgE below 10 U/mL.
Our findings reveal that elevated levels of serum IgE predict airway hyperresponsiveness to histamine in vitro. At the same time, they indicate that the in vitro model of passive sensitization, in addition to its ability to induce allergen responses, also mimics conditions of non-specific airway hyperreactivity, which are relevant under in vivo conditions.