Gene transfer to bone marrow progenitors and to peripheral blood cells 2 months after transplantation. Retroviral vector was produced, purified, and injected into 5-FU–treated mice by DII according to the procedures described in “Materials and methods.” BMCs from saline (control) or MGIN virus–injected femurs were transplanted into primary irradiated recipient mice 24 hours after DII, and PB was analyzed 2 months after transplantation for EGFP expression by flow cytometry (A). In addition, BMCs were obtained from DII-treated 5-FU day-5 animals 24 and 48 hours following injection and plated at 5 × 10⁴ cells per plate in soft agar in duplicate in the presence of IL-3, IL-6, SCF, and granulocyte colony-stimulating factor (G-CSF). Additionally, plating was carried out in the presence or absence of 600 μg/mL G418. Seven days after plating, viable colonies of 50 or more cells were scored. The percentage of G418-resistant colonies was calculated by dividing the number of colonies growing in the presence of G418 by the total number of colonies scored in the absence of G418 (B). The data presented are representative of 3 experiments.