Clearance of transfused KEL2 RBCs occurs in part through FcγR-mediated or C3-mediated pathways. Naïve WT, C3KO, or FcγR KO recipients were passively immunized with PBS or 25 μL of anti-KEL antisera and subsequently transfused with DiI-labeled KEL2 and DiO-labeled WT RBCs. (A) Clearance curves of DiI-positive KEL2 RBCs remaining in circulation posttransfusion in WT or C3KO recipients passively transferred with polyclonal anti-KEL (dashed line) or saline (solid line). (B) Clearance curves of DiI-positive KEL2 RBCs remaining in circulation posttransfusion in WT or FcγR KO animals passively transferred with polyclonal anti-KEL (dashed line) or saline (solid line). These data are representative of 4 (panel A) or 5 (panel B) independent experiments, with 3-5 animals/group/experiment. *P < .05.