Figure 3

Leukemic stem cells express the cell surface target antigen CD52. Upper panels: bone marrow (BM) cells obtained from a patient with acute myeloid leukemia (AML; left panel) or control BM (right panel) cells were stained with antibodies against CD34, CD38, and CD52. The immature CD34+/CD38− stem cells were found to co-express CD52 (red histogram) in the patient with AML but did not express CD52 in the normal BM. The black open histogram represents the isotype-matched control antibody. Lower panels: BM cells were incubated in various concentrations of the CD52-targeted antibody alemtuzumab at 37°C for 1 h. Thereafter, the numbers of viable CD34+/CD38− stem cells were counted by flow cytometry using calibration beads. As visible, exposure to alemtuzumab resulted in a dose-dependent decrease in AML stem cells (left panel) but did not result in a decrease of normal BM stem cells (right panel).