Detection of neo gene by PCR analysis of PB from SCID mice transplanted with HFBM or HFL cells transduced with a retroviral vector. HFBM and HFL cells were transduced with LN, a retroviral vector containing the neo gene as described in the Materials and Methods section and then transplanted into irradiated SCID mice. One month later the mice were bled and the PBMC were assessed for incorporated neo gene by PCR. An ethidium bromide-stained gel showing the presence of the neo primer pair-amplified product in the PBMC of BM-SCID-hu mice (n = 7 mice) and Liv-SCID-hu mice (n = 7 mice) is shown.