IgE-induced passive sensitization of human isolated bronchi and lung mast cells

Passive sensitization of human isolated lung with serum from atopic asthmatic patients provides an opportunity to study the link between airway hyper-responsiveness and the allergic process. To directly demonstrate the role of immunoglobulin E (IgE) in the effect of the atopic serum, we have compared the effect of passively sensitizing both human bronchi and isolated lung mast cells with either serum from atopic asthmatic patients or human monoclonal IgE. Peripheral bronchi ( < 5 mm in internal diameter) were dissected out from human lung obtained at thoractomy and isometric contraction was studied in response to a variety of immunological stimuli according to the sensitization protocol. Mast cells were also isolated from human lung and histamine release was measured under similar experimental conditions. A contractile response was elicited by either the specific antigen or anti-IgE (0.6-600 ng.mL-1) but not anti-immunoglobulin G (IgG) 0.2-20 micrograms.mL-1) in airways sensitized with atopic serum (total IgE concentration of approximately 1,000 international units (IU).mL-1). The maximal contractile response to anti-IgE was 75 +/- 22% of the response to 1 mM acetylcholine. Similarly, anti-IgE released histamine from isolated lung mast cells sensitized with atopic serum up to 22.4 +/- 2% of total histamine measured within mast cells. When isolated airways or mast cells were sensitized with human monoclonal IgE (1,000 IU.mL-1), response to anti-IgE in terms of contractile response or histamine release, respectively, were not significantly different from those obtained following passive sensitization with atopic serum. Finally, the bronchial contractile response to anti-IgE depended not only on the concentration of anti-IgE but also on that of IgE (300-2,000 IU.mL-1) used to sensitize the airways. These results indicate that the effect of antigen or anti-IgE in peripheral bronchi passively sensitized with atopic serum is mimicked when sensitization is carried out directly with human monoclonal IgE.