Proliferative responses of G-CSFR transfectants. Ba/F3 cells stably transfected with the WT or Δ716 G-CSFR were serum and cytokine deprived for 4 hours before cytokine stimulation. Cell proliferation was assayed in the presence of G-CSF or IL-3. The data are expressed as the percent [methyl-³H] thymidine uptake in cells grown in G-CSF versus maximal growth in IL-3 containing media. Error bars represent the standard deviation from three independent experiments.