Transfusion with xenogeneic erythrocytes into SCID mice and their clearance from the circulation

We have previously demonstrated that the red blood cells (RBCs) in the blood circulation of SCID mice could be almost completely substituted with bovine RBCs by means of repeated transfusions. In the present study, transfusion experiments were carried out with RBCs from various animal species to investigate the ability of SCID mice to accept xenogeneic RBCs. Bovine (Bo), equine (Eq), human (Hu) and murine (Mu) RBCs were labeled with a fluorescent dye to trace their trafficking in the blood stream. Following the intravenous injection these RBCs were cleared from the circulation at various rates; the 1/100 reduction time in the labeled cell counts was 2 to 7 days, 4 to 7 hr and 1 to 2 hr with Bo-, Hu- and Eq-RBCs, respectively. In contrast, labeled Mu-RBCs from not only syngeneic but also allogeneic mouse strain were able to stay over 50 days. The difference in clearance rates was attributable to the difference in uptake of the RBCs by the splenic macrophages. The clearance rates of labeled RBCs were significantly decreased by co-transfusion with unlabeled RBCs of the same species, indicating that xenogeneic RBCs were recognized by the reticulo-endothelial system of SCID mice in a species-specific fashion. Furthermore, at least in the case of Hu-RBC, the complement component 3 may play a role in the Hu-RBC clearance in SCID mice since C3 deposition was observed on Hu-RBCs but not on Bo- and Eq-RBCs.