d392 EpoR expressing Ba/F3 cells are not hyperresponsive to Epo when Epo is the only mitogen present. (A) Epo-dose response curves were generated using short-term proliferation assays, with Ba/F3-WT (▪) and Ba/F3-d392 (▴) cells in 10% FCS. (B) Epo-dose response curves were generated using short-term proliferation assays, with the same Ba/F3-WT (▪) and Ba/F3-d392 (▴) cells in SS. (C) Epo-dose response curves were generated using short-term proliferation assays, with DA-3-WT (▪) and DA-3-d392 (▴) cells in 10% FCS. (D) Epo-dose response curves were generated using short-term proliferation assays, with the same DA-3-WT (▪) and DA-3-d392 (▴) cells in SS.