IGE-INDUCED PASSIVE SENSITIZATION OF HUMAN ISOLATED BRONCHI AND LUNG MAST-CELLS

Passive sensitization of human isolated lung with serum from atopic as thmatic patients provides an opportunity to study the link between ah- way hyperresponsiveness and the allergic process, To directly demonstr ate the role of immunoglobulin E (IgE) in the effect of the atopic ser um, we have compared the effect of passively sensitizing both human br onchi and isolated lung mast cells with either serum from atopic asthm atic patients or human monoclonal IgE. Peripheral bronchi (<5 mm in in ternal diameter) were dissected out from human lung obtained at thorac tomy and isometric contraction was studied in response to a variety of immunological stimuli according to the sensitization protocol Mast ce lls were also isolated from human lung and histamine release was measu red 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 mu g . mL(-1)) in airwa ys sensitized with atopic serum (total IgE concentration of approximat ely 1,000 international units (IU). mL(-1)). The maximal contractile r esponse 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 measu red within mast cells, When isolated airways or mast cells were sensit ized with human monoclonal IgE (1,000 IU . mL(-1)), response to anti-I gE in terms of contractile response or histamine release, respectively , were not significantly different from those obtained following passi ve sensitization with atopic serum, Finally, the bronchial contractile response to anti-IgE depended not only on the concentration of anti-I gE but also on that of IgE (300-2,000 IU . mL(-1)) used to sensitize t he airways. These results indicate that the effect of antigen or anti- IgE in peripheral bronchi passively sensitized with atopic serum is mi micked when sensitization is carried out directly with human monoclona l IgE.