IFN-γ reduces HSC maintenance in vitro. HSCs (Lin⁻c-Kit⁺Sca-1⁺CD48⁻CD150⁺) were purified and cultured for 7 days with SCF/TPO/IL-3/IL-6/Flt3-L with or without IFN-γ. Representative plots showing the analysis for progenitors (Lin⁻c-Kit⁺), differentiated cells (Lin⁺), and HSCs (Lin⁻c-Kit⁺CD48⁻CD150⁺) (A) and absolute numbers of these cells (B). Data represent 3 independent experiments with 4 to 5 wells per condition. (C) HSCs from CD45.1 and CD45.1.2 mice were cultured (CD45.1 HSCs without IFN-γ, CD45.1.2 HSCs with IFN-γ), pooled and analyzed, and injected into CD45.2 recipient mice. (D) Representative plots showing donor contribution to total white blood cells and B, T, and myeloid cell lineages in peripheral blood of lethally irradiated CD45.2 recipient mice at 4 weeks after transplantation. (E) Donor contribution to total white blood cells at indicated weeks (n = 8). The experiment was repeated with CD45.1.2 HSCs cultured without IFN-γ and CD45.1 HSCs with IFN-γ with similar results. Mean values ± SEM are shown. *P < .05; **P < .01; ***P < .001. N.D., not detectable; WBC, white blood cells.