Homing and engraftment of bone marrow cells following arterial or venous injection. Equal numbers of differentially labeled cells were simultaneously injected into the tail vein or femoral artery of lethally irradiated mice. The numbers of (A) lin^- or (B) lin+ cells homing to the ipsilateral BM (Ipsil), contralateral BM (Contra), or spleen following intra-arterial (IA) or intravenous (IV) injection were measured by flow cytometry (n = 4 for both groups). (C) The percentage of CD45.1 hematopoietic cells in the ipsilateral and contralateral BM injected via the femoral artery was also measured 6 weeks following injection of the cells (n = 5). Control mice had CD45.1 cells injected into the tail vein. Error bars represent SEM.