Effect of ITs on ex vivo expansion of CD34⁺blood progenitor cells. Varying concentrations of anti–Erb-B2 and anti–EGF receptor IT were added as indicated to ex vivo expansion cultures of CD34⁺ progenitor cells in the presence of SCF, IL-1β, IL-3, IL-6, and EPO. (A) Influence on generation of total nucleated cells at various time points, and (B) on de novo generation of GM-CFU (▪) and BFU-E (□) on day 7 of ex vivo expansion, expressed as numbers of CFU per 3,000 CD34⁺ cells seeded on day 0. Colony assays were conducted in the absence of ITs as described in the Methods. Values are the means ± SD of duplicate determinations. The results shown are representative of at least 4 experiments for each IT with CD34⁺ cells derived from different patients.