Activated ^Q61KN-Ras in combination with IL-4 stimulates the long-term growth of Ba/F3 cells. (A) Ba/F3 or (B)^Q61KN-Ras cells were washed free of IL-3 and incubated in IL-3, IL-4, or media alone with no factor (MA) at a density of 1 × 10⁵ cells/mL. Cells were counted in triplicate at the indicated times and diluted as appropriate to maintain a consistent density of cells. The results are representative of two independent experiments, with two independent clones. Error bars represent the SEM of triplicate samples.