In the mouse model, SMEs are rapidly cleared, accumulate in the spleen, and are processed predominantly by macrophages. (A) Representative normalized frequency plot of projected surface area for long-stored mouse RBCs, as observed at 5 minutes (green line), 2 hours (yellow line), and 24 hours (red line) after transfusion to a syngeneic C57Bl/6 mouse. Control fresh RBCs from a nontransfused mouse (blue) are shown as reference. Dashed black vertical line defines the gating of SMEs. (B) Declining proportion of SMEs in circulation after transfusion (n = 10 mice per group). (C) Variable persistence in circulation of long-stored RBCs (lavender line) that contain the 2 complementary subpopulations of SMEs (black dotted line) and morphologically normal RBCs (light blue solid line), computed by combining flow cytometric and Imagestream data (n = 10 mice per group). (D) Proportion of long-stored RBCs that were cleared 5 to 240 minutes posttransfusion (n = 8 mice per time point). (E) EF 5 to 240 minutes posttransfusion (ratio of transfused CFSE⁺ RBCs in sliced organ/CFSE⁺ RBCs in venous blood; n = 4 mice per time point) in spleen (red line), liver (orange line), and bone marrow (blue line). (F) Posttransfusion erythrophagocytosis of RBCs in spleen (i), liver (ii), and bone marrow (iii), estimated by the increase in CFSE median fluorescence intensity (MFI) of macrophages (red lines), monocytes (blue lines), inflammatory monocytes (purple lines), and granulocytes (orange lines), compared with control nontransfused mice (n = 3 mice per time point). Data are presented as means ± standard errors of the mean. *P < .05, ****P < .0001 by Kruskal-Wallis test compared with fresh RBC condition (B) or by Sidak multiple comparisons test comparing, at each time point, recovery of SME subpopulation vs normal subpopulation (C).