Eosinophil-expressed Notch ligands are functional. (A) Eosinophils were stimulated for 60 minutes with 100 pM GM-CSF in the presence of 10 μM GSI (dotted line) or vehicle alone (heavy line) before permeabilization and detection by flow cytometry of the cleaved, intracellular domain of activated Notch receptor 1. Shaded histogram represents isotype control. (B) RNA was extracted from eosinophils after overnight stimulation with 100 pM GM-CSF in the presence of 10 μM GSI or vehicle control, and analyzed by real-time RT-PCR for the presence of HES1 mRNA. Data are presented as the log 10 of the relative quantification using the GSI-treated sample as the baseline value. Data are from a representative of 3 separate experiments.