Sensitivity of BFU-E erythroid progenitors to Epo.

(A) Hypersensitive response characterized by the in vitro growth of BFU-Es in the presence of low concentrations of Epo (30 and 60 mIU/mL) was found in 6 patients: patient 1 (▴), 2 (▪), 3 (▾), 4(♦), 5 (●), and 6 (■). In patients 2, 3, and 4, small numbers (< 10% of maximum) of colonies were seen in the absence of Epo. (B) Patient 7 (○) and 8 (▵) showed a normal response of BFU-Es to Epo. Dashed lines show the response of erythroid progenitors to Epo of concomitantly tested healthy controls; bars represent the 95% confidence interval.