Time course analysis of monocyte and granulocyte phagocytosis of anti-D–opsonized RBCs. Leukocytes were incubated in duplicate tubes (one at 4°C and the other at 37°C) with either opsonized E coli (A) or anti-D–opsonized RBCs (B) at an RBC/WBC ratio of 500:1 for the indicated times and analyzed 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. ○ indicates monocytes; and •, granulocytes. In panel B, viability (□) of granulocytes was determined by propidium iodide staining. Monocytes gave similar viability percentages (not shown). The results are shown as the means ± SDs of 3 independent experiments. Significance values are indicated (*P < .0001).