Figure 4.
Epo dose-dependent proliferation of Ba/F3 cells expressing wild-type EpoR (EEE) and EPE. Ba/F3 cells growing in IL-3 were infected with retroviruses encoding EEE and EPE receptors. Cells were sorted after 3 or 4 days of proliferation in IL-3 for the top 1% expression of GFP. Pools of cells expressing similar levels of GFP were washed extensively to remove IL-3 and then plated in triplicate in 24-well plates at 1.25 × 105 cells per ml in medium supplemented with Epo (units/ml) as indicated. Cell numbers per ml (mean ± SEM) were recorded after 3 days in culture.