Alternative activation of BMMØs significantly increases levels of phagosomal proteolysis. Alternative activation was achieved by incubating fully differentiated BMMØs with 10 ng/mL IL-4, IL-13, or IL-4 and IL-13 for 48 hours. After uptake of IgG-coupled 3-μm experimental particles, general proteolytic efficiencies of the resulting phagosomes were assessed in real time by measurement of fluorescence liberated from hydrolysis of particle-associated DQ-albumin substrate relative to calibration fluorescence. (A) Real-time representative traces of phagosomal proteolysis. RFU values are proportional to the degree of substrate hydrolysis. (B) Averaged activities relative to untreated controls from 4 independent experiments. Activities were determined by calculation of the slope of the linear portion of the real-time trace (as described by y = mx + c, where y = relative fluorescence, m = slope, and x = time) and expressed relative to untreated controls. Error bars denote SEM. P values were determined by 1-way ANOVA.