Background: We have previously shown that MHC-mismatched fetal liver cells can durably engraft in 45% of nondefective fetal mice, although male donor cells were found in the blood in only 8% of female recipients. We postulated that adult bone marrow stem cells would engraft similarly to fetal liver cells and that postnatal administration of cytokines would recruit donor cells into the peripheral circulation.

Methods: Bone marrow from C57BL/6 adult male mice was injected into allogeneic BALB/c or congenic C57BL/6 fetal recipients that were 11-13 days old. Engraftment was tested by quantitative polymerase chain reaction for the Y chromosome in female recipients (0.0001% sensitivity). Recipients were injected at 1-2 years of age with rat stem cell factor (SCF) and human granulocyte colony-stimulating factor (G-CSF) for 7 days and tested for donor cells in the blood.