Fc-dependence of phagocytosis of anti-D–coated RBCs in monocytes and granulocytes. RBCs were coated with intact anti-D or anti-D F(ab)′₂ fragments and incubated with leukocytes at an RBC/WBC ratio of 500:1 for 2 hours, and phagocytosis in monocytes (A) and granulocytes (B) was measured by flow cytometry. The data are expressed as fold change in phagocytosis and calculated by the formula: percentage of FL2 fluorescence at 37°C/percentage of FL2 fluorescence at 4°C. The results are shown as the means ± SDs of 5 independent experiments. Significance values are indicated (*P < .001).