Siglec-8 ligation induces eosinophil apoptosis. (A) Eosinophils were cultured as indicated, harvested, and analyzed by flow cytometry for annexin-V labeling. Data are mean ± SEM from 6 experiments. (*P ≤ .005; **P ≤ .0005; ***P ≤ .05 for comparison of medium control versus 2E2 + 2° Ab). (B-C) Morphologic changes in eosinophils consistent with apoptosis were observed after 24 hours of 2E2 cross-linking (B) but not after 24 hours of culture in IL-5 (1 ng/mL; panel C). Note in panel B the decreased cytoplasmic volume and condensed, rounded nuclei (arrows) compared with eosinophils in panel C. Data in B-C are representative of 6 experiments (original magnification, × 400).