Recipient preparation for bone marrow transplantation. I. Efficacy of total-body irradiation and busulfan.

The efficacy of total body irradiation and busulfan were studied in recipient preparation for bone marrow transplantation. Male C57BL/6 (B6) mice were prepared for BMT with fractionated TBI or busulfan given in 4 equal doses over 3 days. Both TBI and busulfan are potent stem-cell killers. Both agents resulted in an exponential decrease in CFUs survival with increasing dose down to a 1 x 10(-4) CFUs survival. There appeared to be no break in the curve for either agent. Extrapolated fractional CFUs survival, as related to equivalent donor marrow engraftment or to equivalent 30-day survival without marrow transplantation, appeared lower for TBI as compared to busulfan. This may be due to the effect of busulfan and TBI on different stem-cell populations. Erythroid engraftment was tested after transplanting H-2 compatible LP marrow cells into treated B6 recipients. Greater than 80% of animals demonstrated complete engraftment with 3.4 mg busulfan or 1640 cGy TBI. At these 2 doses, the rate of recovery of donor marrow cellularity and CFUs content in treated recipients were identical for both preparative agents such that a selective effect on the host hematopoietic microenvironment harmful to engraftment was not seen. Complete engraftment in 100% of busulfan-prepared animals could not be achieved as such doses resulted in severe and fatal pulmonary vascular injury at 7-12 weeks posttransplant.