RT-PCR detection of MDR1 in transplant recipient bone marrow. RNA was harvested from bone marrows of the transplanted mice at 14 months. Each RT reaction with 3 μg of total cellular RNA was split into three PCR reactions, these included two parallel analytical reactions and a no primer (no 1°) negative control. PCR conditions were as described for colony RT-PCR. As shown in this autoradiogram, there is low, but detectable, MDR transcript in each of the four transplant recipient mice. Controls include female and male murine spleen RNA from nontransplanted mice, murine bone marrow RNA from nontransplanted mice as negative controls, and RNA from the MDR18.1 producer line as positive control.