IFN-γ increases proliferation and colony formation of primary CD34⁺ stem/progenitor cells from CML patients. (A) Expression of IFN-γ receptor α chain (IFN-γRα) on CD34⁺ stem/progenitor cells from newly diagnosed CML patients. One representative plot of four is shown. (B–E) 10⁴ FACS-sorted CD34⁺ cells from the peripheral blood or BM were cultured in the presence or absence of rh-IFN-γ for 7 d in sextuplicates. At day 7 of culture, BrdU incorporation (B), cell numbers (C), apoptosis (D), and necrosis (E) were assessed in duplicates or triplicates. (F) 2 × 10³ FACS-sorted CD34⁺ cells were cultured in methylcellulose in triplicates and colony-forming capacity was determined after 14 d. Data are displayed as mean ± SEM. Statistics: Student’s t test. **, P < 0.005; ***, P < 0.0001. Apoptotic cells, Annexin V⁺ cells; necrotic cells, Annexin V⁺7-AAD⁺ cells. P, Patient; VEH, vehicle.