Inhibitory effect of c-fos on colony formation by primitive hematopoietic stem cells. Total BM cells or Lin⁻Sca-1⁺ BM cells from Mx–c-fos mice or control littermates were cultured with SCF, IL-3, and IL-6 with various concentrations of IFN-/β. On day 8 of culture, the number of colonies was scored. Results represent mean and SD of four dishes. The data presented are representative of two independent experiments.