Detection of human-derived cells in peripheral blood of transplanted SCID/NOD mice. RNA was extracted from blood leukocytes and used as starting material for RT-PCR. The bands indicate the PCR product corresponding to the human specific β subunit of the GM-CSF receptor. Results are from one untreated mouse and mice treated for 4 weeks with E21R alone and/or MoAb cA2 starting from the time of transplant (early treatment) or starting 4 weeks posttransplant (late treatment). Mouse bone marrow RNA was used as a negative control. The data are representative of two other experiments.