Effects of IL-4 activation on phagosomal acidification in the presence and absence of functional NOX2. Acidification profiles of phagosomes were generated in untreated and IL-4–activated WT and Cybb^−/− BMMØs, with or without NOX2 inhibition with DPI (0.5μM) or vacuolar ATPase inhibition with concanamycin A (100nM). After phagocytosis, pH was calculated from excitation ratios of the pH-sensitive carboxyfluorescein-SE on IgG-coupled beads by regression to a standard curve. (A) Representative real-time phagosomal acidification profiles. (B) Lumenal pH at 30 minutes postinternalization. Graph represents averaged data from 4 independent experiments. Error bars represent SEM. P values were determined by 1-way ANOVA.