Gross hemoglobinuria in wild-type C57BL/6 mice following passive immunization with the IgM E4 anti-hGPA mAb and transfusion with incompatible hGPA-Tg-mRBCs. Mice were passively immunized intravenously with 100 μg of the purified IgM E4 mAb. (A) Representative posttransfusion urine samples were obtained at autopsy from mice receiving incompatible hGPA-Tg-mRBCs (left sample) or receiving compatible wild-type mRBCs (right sample). (B) Urine samples from mice transfused with incompatible hGPA-Tg-mRBCs displayed absorbance peaks at 414 nm (eg, curve A); no absorbance peak at 414 nm was detectable in any urine sample obtained from mice transfused with compatible wild-type mRBC (eg, curve B).