Surface expression of CXCR4 after in vitro culture with plerixafor. Cord blood CD34⁺ HSPCs or PBMCs from normal healthy donors or AML patients were incubated overnight at 37°C in the presence or absence of OP9 stromal cells and plerixafor (1μM) as indicated. Cells were harvested with accutase, washed, stained with Abs to CD45 and CD184 (clone 1D9), and subjected to flow cytometry. Lymphocytes and AML blasts were discriminated by their CD45/SSC characteristics. (A) Relative changes in the amount of cell-surface–expressed CXCR4. RMFI ratios were calculated by dividing the MFI of CD184 by the MFI of a rat IgG2a isotype control. (B) Representative flow cytometric profiles. The flow cytometric histograms show overlays of CXCR4 surface expression on each cell type in the different culture conditions. The data (mean ± SD) are representative of 1 of 2 independent experiments, in which each condition was tested in duplicate or triplicate; *P < .05, **P < .01, ***P < .001.