Fig. 5. Accumulation of sterols in multivesicular endosomes. Dictyostelium cells untreated (A,B) or exposed to U18 for 2 hours (C,D) were fixed and processed for immunofluorescence analysis. Sterols were labeled with filipin (A,C) and cells were also stained with an antibody against p80 to identify endosomal compartments (B,D). Sterols, revealed by filipin, accumulate in p80-positive endosomes in U18-treated cells. The white lines delineate individual cells. Bar, 5 µm.