IFN-γ affects expression of genes involved in cell cycle regulation. (A) Messenger RNA expression levels of cyclin D1 and p57 in HSCs cultured for 24 hours with SCF or SCF and TPO with or without IFN-γ. Expression levels are relative to the expression in SCF/TPO cultured HSCs. Quantitative PCRs were performed in duplicate and data are pooled from 2 independent experiments with 1 to 3 cultures per condition. (B) Messenger RNA expression levels of indicated genes in WT and IFN-γR1^−/− HSCs from chimeric mice 8 days after LCMV infection. Expression levels are relative to the expression in WT and IFN-γR1^−/− HSCs from naive WT: IFN-γR1^−/− chimeric mice. Quantitative PCRs were performed in duplicate of 2 or 3 pooled samples of purified HSCs. Mean values ± SD are shown. *P < .05; **P < .01.