Increased hypodense eosinophils after activation with PAF-acether and calcium ionophore in asthmatic subjects

Eosinophils play a major role in the pathogenesis of bronchial asthma. In this study, we examined the density characteristics of blood eosinophils from 9 normal healthy individuals and 9 allergic asthmatic patients. Furthermore, the effect of platelet-activating factor, a potent mediator of inflammation, and calcium ionophore, A23187, on the density of normodense eosinophils (density > 1.085 g/ml) has also been examined. Initially, asthmatic patients had 27.0 ± 1.1% eosinophils of lighter density (density ≤ 1.081 g/ml), significantly greater than that in the normal individuals (7.5 ± 0.5%). After exposure to platelet-activating factor (1 μM) or calcium ionophore (A23187, 1 μg/ml), the normodense eosinophils switched to hypodense in both groups: 16.7 ± 2.1% and 54.2 ± 3.7%, respectively, in normal individuals, and 30.6 ± 5.7% and 77.4 ± 2.3%, respectively, in asthmatic patients. These data demonstrated that a certain percentage of normodense eosinophils from asthmatics and normal subjects switched to hypodense after activation with platelet-activating factor or calcium ionophore. Furthermore; eosinophils from asthmatics switched to a greater degree than in normal subjects, suggesting that the normodense eosinophils in asthmatics become primed probably by endogenously released mediators.