Long-term culture of the Ba/F3 cells transfected with pCMX-Δ(5-195)GCRER in the presence of 10 U/mL of rmIL-3 (○) or 10⁻⁷ mol/L of β-estradiol (▴). The rmIL-3– and β-estradiol–containing cultures were diluted to the cell concentration of 5,000 cells/mL every 3 and 4 days, respectively, as shown in lower line graphs. Upper line graph shows cumulative data during the culture period. Twenty-one days later, cells in the β-estradiol–containing cultures were washed (arrow) and further cultured in the (▴) presence or (•) absence of β-estradiol. Cell proliferation was estimated using XTT assay.