Effect of anti-CSF1R mAb treatment on myeloid populations within lymphoid tissues. (A) Peritoneal lavage cells from anti-CSF1R and rat IgG-treated mice stained with phycoerythrin (PE)–conjugated F4/80. Bone marrow, blood, and splenocytes were counted (B) and cell populations enumerated using 3-color flow cytometry (C). (D) Flow cytometric analysis of EGFP, F4/80, and Gr-1 expression on blood mononuclear cells. In the top panel, the R3 gate contains monocytes that express 3-4-fold higher F4/80 and csf1r-EGFP, and are completely absent after antibody treatment. In the bottom panel, the R2 gate contains granulocytes, which express both Gr1 and csf1r-EGFP. These cells can also be seen in the top panel, ungated, expressed csf1r-EGFP, but not F4/80. The R3 gate contains Gr1-positive monocytes, and the R4 gate, Gr1-negative monocytes. Histograms at right compare the frequency of EGFP⁺F4/80^high and EGFP⁺Gr-1^neg in blood from rat IgG and anti-CSF1R treated MacGreen mice (white and black bars, respectively). Results shown are from 1 of 2 independent experiments, where n = 4-5 animals per group. A value of P < .05 was considered statistically significant (*).