Eosinophil infiltration in lung tissue is one of the characteristic features of bronchial asthma. Such cell infiltration seems to be induced by the eosinophil chemotactic factor (ECF). PAF and IL-5 are potent chemoattractants and activators for eosinophils. To evaluate the reactivity of eosinophils in asthmatics under various conditions, the migratory function of eosinophils to PAF and IL-5 was investigated by the modified Boyden chamber method. Eosinophils of asthmatics were highly purified using a flow cytometric method previously reported. The migratory response of the eosinophils of asthmatics was greater than that of healthy suljects. Eosinophils from atopic asthmatics showed a higher response to PAF than those from non-atopic asthmatics. Eosinophils in the attack stage showed a higher response than those in the non-attack stage. Hypodense eosinophils showed an increased migratory response. The migratory response was correlated to the serum concentration of ECP and blood eosinophil count. These findings suggest that the reactivity of eosinophils is heterogenous and relates to the degree of eosinophilia, and that IL-5 as well as PAF plays an important role in the pathogenesis of bronchial asthma
