IL-4–activated BMMØs have increased phagosomal levels of mature cathepsin S and L. (A) Average mRNA expression level relative to controls from 5 independent QPCR experiments. Relative expression was expressed as mRNA levels normalized to 18S and presented relative to untreated BMMØs. Error bars denote SEM. P values were determined by 1-way ANOVA. (B) Cysteine cathepsin activity of whole-cell lysates from untreated and IL-4–activated WT and Cybb^−/− BMMØs was measured in vitro by the use of a fluorogenic substrate of cathepsin B, S, and L. Graphs represent averaged rates relative to untreated WT sample from 4 independent experiments. Error bars represent SEM. P values were determined by 1-way ANOVA. Relative abundance of the aspartic cathepsin D and the cysteine cathepsins B, S, and L were determined in whole cell lysates of untreated and IL-4–activated WT BMMØs by standardized semiquantitative Western blotting. (C) Representative images of western blots. Mature forms of cathepsins B, S, and L and intermediate form of cathepsin D are shown. (D) Average of band relative density from 3 independent Western blot experiments. Relative abundance of the aspartic cathepsin D and the cysteine cathepsins B, S, and L were determined in phagosomes isolated 60 minutes after particle uptake by untreated and IL-4–activated WT BMMØs by standardized semiquantitative Western blotting. (E) Representative images of western blots. Mature forms of cathepsins B, S, and L and intermediate form of cathepsin D are shown. (F) Average of band relative density from 5 independent Western blot experiments. Relative density was determined by calculation of pixel volume for treated sample relative to untreated BMMØ sample using Quantity One analysis software (Bio-Rad). Error bars denote SEM, P values were determined by paired t test.