Flow cytometric histogram analysis of phagocytosis of anti-D–opsonized RBCs by granulocytes and monocytes. Leukocytes were incubated in duplicate tubes (one at 4°C and the other at 37°C) with anti-D–opsonized RBCs at an RBC/WBC ratio of 500:1 for 2 hours and analyzed by flow cytometry (A). Panel B shows the CMTMR FL2 fluorescence of gated monocytes (panel A, R1 gate), whereas panel C shows the CMTMR FL2 fluorescence of gated granulocytes (panel A, R2 gate) incubated at the indicated temperatures (thin line, 4°C; thick line, 37°C). The data shown are from one representative experiment.