Development of lineage-specific colonies from CD34⁺ blood progenitor cells in the presence of anti–Erb-B2 and anti–EGF receptor IT. A total of 3,000 CD34⁺ cells were inoculated into IL-3, GM-CSF, and EPO supported soft-gel assays and evaluated for GM-CFU (▪) and BFU-E numbers (□) in a light microscope on day 14. Values are the means ± SD of duplicate determinations. Results shown are representative of at least four experiments in each case (ie, anti–Erb-B2 and anti–EGF receptor IT) with CD34⁺ cells derived from different patients.