Experimental design. Recipient mice received a passive immunization with 1 μg of anti-HOD monoclonal antibody (anti-HOD mAb), nonspecific mAb, or PBS control followed by an RBC transfusion. Each transfusion consisted of 100 μL of packed leukoreduced RBCs at 20% hematocrit, with 50 μL of allogeneic HOD RBCs, and 50 μL syngeneic B6 RBCs, labeled with DiO and DiI lipophilic dyes, respectively. Before transfusion, labeled HOD-DiO and B6-DiI RBCs were mixed at a 1:1 ratio and analyzed on a flow cytometer to determine the pretransfusion ratio. After transfusion, RBCs and sera were collected from experimental mice and used to determine RBC survival and alloantibody production.