Antibody-induced antigen loss requires the FcγIII receptor. C57BL/6 mice (A-D) or mice with targeted deletions of either FcγIIIR (E-H) or FcγIIR (I-L) received an intravenous injection of HEL/CFA immune serum. Six hours later, each group was transfused with a mixture of leukoreduced CM-DiI–labeled mHEL RBCs and DiO-labeled C57BL/6 RBCs. Four days after transfusion, peripheral blood was harvested, and antibody coating of RBCs was measured by gating on transfused mHEL (CM-DiI⁺) or C57BL/6 (DiO⁺) cells and staining with anti–mouse Ig. Remaining HEL antigen was measured by staining with anti-HEL. Solid line indicates gating on mHEL RBCs; and dotted line, gating on B6 RBCs. The experiments shown in this figure have been reproduced in at least 3 separate experiments. The data presented in this figure are representative results.