Transfusion of mHEL RBCs into HEL/CFA-immunized mice results in loss of HEL antigen without clearance of mHEL RBCs. C57BL/6 mice were immunized with HEL/CFA or OVA/CFA. Immunized mice then received transfusions of a mixture of leukoreduced CM-DiI–labeled mHEL RBCs and DiO-labeled C57BL/6 RBCs. Peripheral blood was obtained at the indicated time points. The remaining percentages of transfused mHEL or C57BL/6 RBCs (given in graphs) were determined by detecting residual-labeled RBCs by flow cytometry (A). At the indicated time points, peripheral blood was stained with anti–mouse Ig, and the amount of immunoglobulin coating RBCs was determined by gating on transfused mHEL or C57BL/6 RBCs and measuring bound anti–mouse Ig by flow cytometry (B). Levels of HEL antigen were measured by staining with anti-HEL followed by anti–mouse Ig and comparing staining on transfused mHEL or C57BL/6 RBCs (C). The experiments shown in this figure have been reproduced in at least 3 separate experiments. The data presented in this figure are representative results.