Kinetic study of eosinophil apoptosis and its relationship to Th2 cytokines in asthmatic murine model.

OBJECTIVE: To investigate the significance and regulatory mechanism of eosinophil apoptosis in asthmatic airway inflammation using an animal models, as well as its relationship to IL-5 and IL-10. METHODS: An animal model of asthma was established by ovalbumin (OVA) sensitizing-challenging BALB/C mice. At seven points in the time course after challenge, bronchoalveolar lavage (BAL) was performed to obtain BAL cells. Levels of two Th2 cytokines, IL-5 and IL-10 were detected by ELISA. A double label technique combining CD15 with CD49d was used to distinguish eosinophils from other cell types. Cell apoptosis was assayed by PI stain using a flow cytometer. RESULTS: Eosinophil apoptosis was identified and a two-phase elevation of apoptosis percentages was observed, although no significant difference was found between average apoptosis in the asthmatic group and that in the control. Analysis of kinetic changes of eosinophil apoptosis and cytokine levels revealed a negative correlation between apoptosis percentages and levels of IL-5, and a closer correlation between apoptosis percentages and the IL-5/IL-10 ratio. Dexamethasone pretreatment markedly reduced IL-5 levels in BAL, elevated eosinophil apoptosis percentages, but had no effect on IL-10 levels. CONCLUSION: Eosinophils underwent apoptosis in asthmatic airways. Equilibrium between IL-5 and IL-10 not only regulated eosinophil infiltration, but also modulated cell apoptosis.