Homing of CFU-S in BM and spleen. BM and spleen cells of primary irradiated recipients, injected with 10⁷ BM cells in PBS (▪) or mixed with 200 mg the listed antibodies (▨) or Meca-89 (□) 3 hours before killing, were administered to secondary irradiated recipients. The spleen of the secondary recipients were obtained 12 days later for spleen colony counting. The number of CFU-S found in one leg or the spleen of primary recipients was calculated and represents the mean ± SEM of two to four experiments. * P < .05.