Progression of cytokine-stimulated Lin⁻ Rho^low/Ho^low cells through G₀ /G₁ and into S phase. Lin⁻ Rho^low/Ho^low were incubated in medium containing a cocktail of either 4 cytokines (IL-3, IL-6, IL-11, and SCF; A) or 7 cytokines (IL-3, IL-1α, GM-CSF, G-CSF, SCF, FGF, and CSF-1; B), and at indicated intervals duplicate aliquots of cells were analyzed for ³H-thymidine incorporation followed by autoradiography to assess the percentage of cells with labeled nuclei as described in the Materials and Methods. Each set of symbols in (A) represents observations from separate individual experiments.