Serum immunoglobulin E levels predict human airway reactivity in vitro

Background Airway hyperresponsiveness to non-specific stimuli is one charac teristic feature of airway diseases such as bronchial asthma and chronic br onchitis. Until now, studies aiming to demonstrate a relationship between i n vivo conditions associated with airway hyperreactivity and in vitro airwa y responsiveness have been inconclusive. Objective Since serum immunoglobulin (Ig) E is believed to be one determina nt of airway reactivity in vivo, we studied whether in vitro airway reactiv ity 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 s mooth muscle reactivity in vitro. Methods Bronchial rings from nine patients with total serum IgE levels abov e 200 U/mL and 10 patients with total serum IgE levels below 10 U/mL were p assively sensitized, i.e. incubated overnight with buffer or sensitizing se rum containing high levels of total IgE (> 250 U/mL). Afterwards, contracti le responses to histamine were assessed in the organ bath. Results Histamine responsiveness was significantly increased in airways obt ained 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 sensitizat ion of bronchi from patients with low IgE significantly increased histamine responsiveness, as compared with non-sensitized controls from the same pat ients (P < 0.05). In contrast, passive sensitization of airways from patien ts with elevated IgE did not further increase responsiveness. There was no difference in histamine reactivity between non-passively sensitized and pas sively sensitized tissue preparations from patients with IgE above 200 U/mL and passively sensitized tissues from patients with IgE below 10 U/mL. Conclusion Our findings reveal that elevated levels of serum IgE predict ai rway hyperresponsiveness to histamine in vitro. At the same time, they indi cate that the in vitro model of passive sensitization, in addition to its a bility to induce allergen responses, also mimics conditions of non-specific airway hyperreactivity, which are relevant under in vivo conditions.