BFUe colonies stimulated by MoAb34 and EPO. Purified CD34⁺ cells from human peripheral blood were incubated for 20 days. BFUe colonies were identified by microscopic examination and photographed. Representative colonies obtained at 2 different concentrations of EPO and MoAb34, respectively, are shown. (A) 144 nmol/L MoAb34; (B) 36 nmol/L MoAb34; (C) 130 pmol/L EPO; (D) 6.6 pmol/L EPO.