CFU-E– and BFU-E–derived colony formation by CCR1 positive or negative normal BMMNCs in the presence of Epo plus SCF. The purified CCR1 positive or negative normal BMMNCs were plated in a methylcellulose medium containing Epo and SCF. The numbers of CFU-E (open bar) and BFU-E (closed bar) were determined at day 7 or day 14 of culture, respectively. The data are representative of three independent experiments with quadruplicate determinations.