Phagocytosis of anti-D–opsonized RBCs by monocytes and granulocytes. Leukocytes were incubated in duplicate tubes (one at 4°C and the other at 37°C) with anti-D–opsonized RBCs at the indicated ratios for 2 hours, and phagocytosis was 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. The results are shown as the means ± SDs of 5 independent experiments. Significance values are indicated (*P < .001).