Antigen expression patterns of stem and progenitor cells. Expression of cell surface antigens on CD34⁺/CD38⁻ stem cells and CD34⁺/CD38⁺ progenitor cells obtained from normal BM or from patients with AML or CML (all samples obtained at diagnosis). A total of 239 patients with AML (range, 3-172 per marker; median, 29 per marker), 81 patients with CML (range, 3-73 per marker; median, 17 per marker), and 36 normal BM samples (range, 3-25 per maker; median, 8 per marker) were analyzed. Surface expression was analyzed by multicolor flow cytometry as described in supplemental Flow cytometric analysis. Results are expressed as mean of all donors and represent the staining index, which was calculated from median fluorescence intensities that were obtained with the test antibodies and isotype-matched control antibodies.