Immunoprophylaxis with anti-KEL sera leads to less RBC clearance in FcγR KO × C3 KO (double-KO) recipients compared with wild-type, FcγR KO, or C3 KO recipients. Posttransfusion clearance curves of KEL RBCs in (A) wild-type, (B) FcγR KO, (C) C3 KO, and (D) FcγR KO × C3 KO (double-KO) recipients, in the absence (solid line) or presence (dashed line) of immunoprophylaxis, to 24 hours. These data are representative of 2 or 3 independent experiments with 3 to 5 mice per group per experiment; error bars indicate SD between individual mice. (E) Comparison of percentage of KEL RBCs remaining between 10 minutes and 24 hours after transfusion (left) or 10 minutes and 5 days after transfusion (right) in the presence of anti-KEL immunoprophylaxis; *P < .05 by 2-way ANOVA between double-KO and all other recipients.