HOD RBCs colocalize with MZ B cells within the marginal sinus of the spleen following transfusion. HOD RBCs were isolated and stained with DiO, resulting in a fluorescently distinct population. (A-B) PBS (A) or DiO-labeled HOD RBCs (red) (B) were injected into HOD⁻ B6 recipients, followed by splenic harvest 24 hours after transfusion and immunofluorescent staining of FO B cells (IgD; yellow) and MZ B cells (CD1d; blue). Samples were analyzed using a Leica SP8 multiphoton confocal microscope with a ×10 (A-B) or ×40 (C) objective. The white box in panel B is magnified in panel C. White arrows indicate examples of colocalization of transfused HOD RBCs with MZ B cells. Scale bars, 100 μm. Representative data are shown from experiments reproduced 2 or 3 times, with 3 mice per group per experiment.