Flow cytometry analysis of MDR1 gene expression in chimeric mice.

(A) Five weeks after transplantation of MDR1-transduced and mock-transduced CD34+ PBPC samples (NOD/SCID set 10), chimeric-mouse BM cells were obtained and analyzed for the presence of human leukocytes (CD45+) and MDR1 expression (Rh-123 efflux) by FACS after staining with rhodamine-123 (Rh-123), phycoerythrin (PE)-conjugated antihuman CD45 antibody and propidium iodide (PI). The proportions of live-gated viable human CD45+ cells expressing theMDR1 gene (Rh-123^dull cells) that were detectable in 2 representative mice injected with transduced CD34+ PBPC and in a control mouse into which mock-transduced CD34+ PBPC was transplanted are shown. (B) MDR1 expression in the in vitro myeloid progeny of human cells recovered from the corresponding chimeric mice (upper panel). Human cells selectively enriched from freshly isolated chimeric-mouse BM cells by immunomagnetic depletion of the mouse BM cells were subjected to a 10-day liquid culture in the presence of a myeloid differentiation-inducing cytokine mixture and subsequently analyzed by FACS after staining with Rh-123, PE-conjugated antihuman CD33 antibody, and PI. The proportions of human myeloid (CD33+) Rh-123^dull cells are indicated in the right corner of each plot.