What Determines Asthma Phenotype? Is It the Interaction between Allergy and the Smooth Muscle?

Passive sensitization provides a useful model for the examination of the effect of the allergic process on smooth muscle reactivity and growth. This technique involves the incubation of bronchial tissue segments or bronchial smooth muscle cells in culture with serum from patients with allergic asthma or, alternatively, serum from nonallergic nonasthmatic patients. The allergic serum contains a high concentration of total IgE, usually greater than 1,000 IU/ml, and is taken from patients who exhibit a positive skin test response to one or more common allergens, whereas control nonallergic serum has a total IgE concentration of less than 20 IU/ml and is derived from patients who are skin test negative (1). One of the major advantages of this model is that comparisons can then be made between tissues or cells from the one patient, thus minimizing the inevitable variability in between-patient responses so familiar to those who work with human tissue.