510 Caspase-9 is Involved in CD30 Activation Induced Eosinophil Apoptosis

BACKGROUND: We evaluated whether ligation of CD30 incite the apoptosis, and investigated the mechanisms of CD30 induced eosinophil apoptosis is dependent on caspase activation. METHODS: We purified eosinophils using MACS system. Expression of CD30 on eosinophils were measured and eosinophils were cultured in the wells pretreated with anti-CD30 mAb and isotype control IgG1, IL-5 and dexamethasone in RPMI 1640 media supplemented with 10% FBS, and the apoptotic rate were measured using flow cytometry. To evaluate whether caspase-9 is involved in CD30- induced eosinophil apoptosis, the apoptotic rate was evaluated with addition of caspase-9 inhibitor and the expression of procaspase-9 was also measured using Western blot. RESULTS: The apoptotic rates of eosinophils cultured in the presence of anti-CD30 mAb were significantly increased to 29.1 ± 6.1% and 47.3% ± 4.7% compared with 17.1 ± 6.7% and 29.4 ± 9.2% of the control at 4 and 24 hours, respectively (both P < 0.05). Caspase-9 inhibitor suppressed the mAb induced eosinophil apoptosis from 54.8 ± 6.9% and 71.5 ± 11.6% to 24.5 ± 6.0% and 47.8 ± 11.4% at 18 and 36 hours, respectively (both P < 0.001). We also showed the expression of procaspase-9 with the mAb was diminished compared with that of the control and of IL-5. CONCLUSIONS: This study showed CD30 activation enhances the eosinophil apoptosis and the effect is mediated by Caspase-9 activation.