Ly6C^himonocytes emigrate from the bone marrow and home to the spleen after transfusion of old RBCs. Wild-type C57BL/6 mice were transfused with 350 μL of fresh or old RBCs and sacrificed at defined time points. (A) Flow plots depict increases in Ly6C^hi monocytes in the blood and spleen and a decrease in the bone marrow at 5 hours posttransfusion. (B) Quantification of circulating Ly6C^hi monocytes at defined time points demonstrating increased levels at 5 hours posttransfusion. (C) Quantification of bone marrow Ly6C^hi monocytes demonstrating decreased levels at 5 hours posttransfusion. (D) Splenic Ly6C^hi monocyte levels increase substantially at 5 hours posttransfusion. (E) Histogram of Ki67 staining of splenic Ly6C^hi monocytes at 5 hours posttransfusion. Data representative of 3 experiments with at least 3 mice per group. *P < .05; **P < .01; ****P < .0001; ANOVA followed by Tukey posttest.