Purification and ⁸⁹Zr-oxine labeling of rhesus blood eosinophils. (A) Flow cytometric analysis with cell surface staining for CD16, Siglec-8, VLA4, or CD64 in human and rhesus whole-blood samples. Representative plots are shown for each marker. (B) Representative dot plots show flow cytometric analysis with cell surface staining for VLA4 or CD64 followed by intracellular staining for EPX in rhesus granulocytes. (C) A representative image shows nuclear and cytoplasmic morphology of rhesus eosinophils after purification. (D) Eosinophil purity in the CD64-negative rhesus granulocyte fraction. Shown is the relative abundance of 5 WBC types in the purified cell fraction in 5 independent experiments. Error bars represent mean ± SD. (E-H) Apoptosis, viability, activation, and migration assays measured by flow cytometry in purified rhesus eosinophils, with or without ⁸⁹Zr-oxine labeling: percentage of cells positive for the early apoptosis marker annexin V (E), in 4 independent experiments; percentage of nonviable cells, defined as cells positive for both annexin V and propidium iodide, in 4 independent experiments; (G) percentage of cells positive for the activation marker CD69, in 3 independent experiments (F); and in vitro migration of purified rhesus eosinophils, with or without ⁸⁹Zr-oxine labeling (H), toward control (no chemokine) or recombinant rhesus CCL11. The percentage of cells that migrated toward CCL11 on a Transwell assay after 2 hours of incubation, in 4 independent experiments, is shown. Statistical analysis of the data in panels E-H was performed with the paired Student t test.