Long-term analysis of engraftment with donor BM in nonirradiated recipients. HW80 recipient mice were injected for 5 consecutive days with transduced BM cells (C57) that had been expanded in culture for 12 to 16 days. Later the same day, mice were treated with trimetrexate (130 mg/kg) and NBMPR-P (20 mg/kg). Beginning at 1 week posttransplant, donor C57 Hb levels were quantitated by electrophoresis on cellulose acetate gels. Persistent engraftment was only seen in mice receiving expanded BM cells transduced with MDR1 (5 of 12). Engrafted mice included: MDR 7 (▪), MDR 11 (▴), MDR 18 (⧫), MDR 20 (▾), and from the second experiment MDR 15 (•). No stable engraftment was seen with mock-transduced (0 of 8) or DHFR-transduced (0 of 8) expanded BM. Engraftment levels in mice receiving mock-transduced BM (+ symbol) were low to undetectable, thus many of these symbols are not seen on the graph. Mice without evidence of long-term engraftment are indicated with open symbols. Shown are mice from two separate expansion experiments.