Mapping study of colony formation by primitive hematopoietic stem cells. Lin⁻Sca-1⁺ BM cells (1 × 10²) from Mx–c-fos mice or control littermates were cultured with SCF, IL-3, IL-6, and Epo. IFN-/β (200 U/mL) was added on day 0, or on day 0 and day 4. Graphic presentation indicates cell number changes in individual colonies that later became a mixed colony (CFU-Mix). The data represent colonies identified in two plates. The data presented are representative of two independent experiments.