Expression of the CXCR4 receptor on megakaryocytic leukemia cell lines. Cells were stained with a PE-conjugated anti-CXCR4 MoAb or isotype control antibody and then analyzed by flow cytometry. The staining with control antibody is shown as the solid profile and the staining with the anti-CXCR4 antibody is shown as the thin line. The percentage of positive expression is provided in the inset. MFI, mean fluorescence intensity.