Anti-KEL antibodies induce clearance of KEL2 RBCs. Naïve WT recipients were passively immunized with phosphate-buffered saline (PBS) or titrated amounts of anti-KEL antisera and subsequently transfused with DiI-labeled KEL2 and DiO-labeled WT RBCs. (A) Gating strategy of DiI-positive KEL2 or DiO-positive B6 RBCs. (B-C) Clearance was determined by calculating the ratio of DiI-labeled KEL2 to DiO-labeled WT RBCs after passive antibody transfer. (D) Serum cytokines 2 hours posttransfusion. (E) Heme in serum and (F) heme in urine posttransfusion. (G) Wright-Giemsa–stained blood smears. These data are representative of 2 independent experiments, with 3-5 animals/group/experiment; error bars indicate standard deviation. *Statistical significance, P < .05.