SMEs are rapidly cleared when perfused through human spleen ex vivo. (A) Kinetics (means ± standard errors of the mean) of the normalized concentration in the perfusate of human spleen ex vivo (n = 7) of 14 RBC concentrates stored for 35 to 42 days and rejuvenated (RW; dashed line) or not (NT; solid line). (B) Representative normalized frequency plot of the projected surface area of RBCs stored for 42 days before (solid red histogram) and after (dotted line) rejuvenation. Dashed vertical line defines the gating cutoff for SMEs. (C) Representative frequency plot of projected surface area of stored RBCs (37 days) before (red histogram) and at different time points after perfusion through human spleen ex vivo (0 minutes, solid blue line; 2 minutes, solid green line; 20 minutes, dotted black line; and 40 minutes, dashed orange line). (D) Proportion of SMEs at the beginning (T0) and mean proportion of SMEs at all observations between 40 and 70 minutes (T40-70min) of perfusion through human spleen ex vivo (n = 6; red dashed line represents mean). (E) Correlation between mean retention rate in human spleen perfused ex vivo and proportion of SMEs in the RBC concentrate before transfusion (n = 28; P = .03; Spearman r = 0.5; r² = 0.2). *P < .05, **P < .01 by Sidak multiple comparisons test comparing, at each time point, the persistence in circulation of rejuvenated vs nontreated RBCs (A) or by paired Student t test comparing proportion of SMEs at T0 vs T40-70min (D).