Baseline RBC velocity (V_RBC) of XRITC-labeled sickle RBCs injected into mouse recipients expected to have different levels of endothelial P-selectin expression. CAIM flow data from visualization of 20 to 40 μm diameter mucosal-intestinal venules are represented as the average V_RBC of XRITC-labeled RBCs. Labeled sickle RBCs were injected intravenously into C57BL/6 (control; n = 24), P-selectin knock-out (P-sel k/o; n = 9), and sickle cell mice (n = 10). The error bars indicate the standard error of the mean. ^* indicates a statistically significant (P < .05) difference from the other groups.