Delayed clearance of porcine RBCs in CD47 KO compared with WT mouse recipients. CFSE-stained pig RBCs (2 × 108) were intravenously injected into CD47 KO (n = 5) or WT (n = 5) mice. (A) Blood was collected at the indicated time points and the percentages of injected pig RBCs were analyzed by flow cytometry. (Top) Representative fluorescence-activated cell sorter (FACS) profiles showing percentages of porcine RBCs in the blood at the indicated times. Numbers indicate the percentages of CFSE+ porcine RBCs. (Bottom) Percentages (mean ± SDs) of porcine RBCs in blood, which were normalized with the levels at 15 minutes after injection as 100%. Results from 2 experiments are combined. *P < .01; **P < .001. (B) Spleens were harvested from CD47 KO (top row, × 100) and WT (middle row, × 100; bottom row, × 200) at 1 hour after injection of CFSE-stained pig RBCs (green), and frozen spleen sections were stained with anti-F4/80 mAb (red). Engulfment was seen as a yellow event after merging the green-filtered and red-filtered images (right column). Three mouse recipients from each group were examined and representative results are shown.
