Normal surface expression of CD16 and ¹⁰N-nonyl acridine orange (NAO) staining in freshly isolated granulocytes from patients with BHTS. Fresh granulocytes from a control individual (left) and from a BTHS patient (right) were colabeled with annexin-V–FITC and anti-CD16–PE mAb (top; representative for 7 controls and patients tested) or stained with NAO (bottom; representative for 3 controls and patients tested) and analyzed by flow cytometry. In the top panels, CD16^–/dull cells (circles) were identified as eosinophils by separate staining with anti-CD9 mAb (a specific eosinophil marker) and morphology of cytospin preparations (data not shown). In the bottom panels, values indicate mean fluorescence intensity (MFI) of NAO staining.