Effect of IL-5 and GM-CSF on Siglec-8 cross-linking–induced eosinophil death. (A) IL-5 (1 ng/mL) was added at the beginning of the cell culture and viability was determined at various time points as indicated. Data are from 4 to 6 experiments. *P < .05; **P < .0005. (B) IL-5 or GM-CSF (each at 30 ng/mL) reduces the concentration of Siglec-8 mAb needed to induce maximal eosinophil apoptosis. Eosinophils were initially cultured with IL-5 or GM-CSF in the presence of secondary Ab and the indicated concentrations of 2E2. After 24 hours, apoptosis was analyzed using annexin-V staining. Data are presented as mean ± SEM from 4 experiments. *P < .05; **P < .0005; ***P < .005.