Effect of IL-9 on eosinophil survival.

(A) Percentage of apoptotic eosinophils from different patients treated for 18 hours with IL-9 (solid bar), IL-5 (broken bar), or medium alone (open bar). Morphological assessment was performed as described in “Materials and methods.” (B) There was no significant difference in cell viability observed between the 3 culture conditions at 18 hours, as assessed by trypan blue exclusion. (C) Morphological alteration of nuclei was evaluated by Diff Quick staining. Freshly purified peripheral blood eosinophils stimulated with 10 ng/mL IL-9 (panel ii) or IL-5 (panel iii) showed less apoptotic cells (indicated by arrows) compared to medium alone (panel i). (D) Similar results were obtained using either morphology assessment (M) or DNA fragmentation assay using PI and flow cytometry analysis. DNA fragmentation was assessed by analysis of the staining characteristics of fixed permeabilized cells exposed to the DNA-binding dye, PI. Analysis was performed by flow cytometry on a FACScan machine. The data are the mean ± SD of 3 independent experiments.