IFN-γ impairs proliferation of HSCs. Purified HSCs (Lin⁻c-Kit⁺CD48⁻CD150⁺) were labeled with CFSE and cultured for 4 days with SCF/TPO/IL-3/IL-6/Flt3-L with or without IFN-γ. (A) Expansion of total cells in culture relative to day 1. (B) Expansion of HSCs (Lin⁻c-Kit⁺CD48⁻CD150⁺) relative to day 1. Histograms (C) and division index (defined as the average number of divisions that a cell that was present in the starting population has undergone) (D) of CFSE-labeled HSCs cultured with or without IFN-γ. (E) Representative plots showing percentage of HSC (Lin⁻c-Kit⁺CD48⁻CD150⁺) in cultures and (F) quantification of these data. Histograms and plots are representative of 3 independent experiments. Graphs represent data pooled from 3 independent experiments with duplicate cultures. Mean values ± SEM are shown. *P < .05; **P < .01; ***P < .001.