Fig. 3. Efficiency of phagocytosis of stiff or soft objects during Fc-receptor-mediated phagocytosis. (a) Stiff polyacrylamide beads (left two bars) are six times more likely to be phagocytosed than soft beads (right two bars). Beads without antibody coating are poorly phagocytosed. Phagocytic index is defined as the average number of beads internalized per cell. These data were compiled from six independent experiments with 100 cells counted in each experiment. (b) Frustrated phagocytosis on progressively softer opsonized polyacrylamide sheets. Data were compiled from three independent experiments. Stiff sheets cause sixfold more cells to undergo frustrated phagocytosis than do soft sheets. Error bars indicate the standard deviation between experiments. Panels c-e show images of macrophages phagocytosing opsonized stiff beads (c-d) and sheets (e). Internalized beads can be easily discriminated from beads that are merely attached to the cell surface based on fluorescence and phase images. Panels f-h show cells that failed to phagocytose opsonized soft beads (f-g) or sheets (h). Bar, 10 µm.