Role of α4 integrin, PSGL-1, and E-selectin ligands in HPC homing to bone marrow. Lethally irradiated wild-type (WT) or E-selectin–deficient (E^–/–) mice were injected with antibody-treated wild-type donor BM cells. CFU-Cs were determined from the recipient BM and spleen 3 hours after injection. (A) Transplantation of donor cells treated with rat IgG, anti–α4 integrin (PS/2), anti–PSGL-1 (4RA10), or both PS/2 and 4RA10 into WT recipient mice. n = 6 mice per group. (B) Transplantation of antibody-treated donor cells into E^–/– recipient mice. n = 5 per group. *P < .05, **P < .01 compared with rat IgG control group.