Analysis of surface antigens and the number of clonogenic cells after 2 weeks' expansion of CB-derived CD34⁺ cells on control or Ihh stromal cells. (A) Expression of surface antigens on ex vivo–expanded hematopoietic cells. The x-axis indicates CD34 labeled with a FITC-conjugated monoclonal Ab. The y-axis indicates CD11b labeled with a PE-conjugated monoclonal Ab. Positivity for a surface antigen was defined with the use of the isotype control monoclonal Ab. Data shown are from 1 representative experiment of 4 showing similar results. IgG1 indicates immunoglobulin G1. (B) Ex vivo expansion of clonogenic cells in CB CD34⁺ cells for 2 weeks. Values indicate the number of clonogenic cells for Ihh stroma versus control stroma. *P < .05 versus control. **P < .01 versus control. The number of CFU-Cs and CFU-Mix's before the culture were 1412 ± 369 and 37.5 ± 7.8, respectively, out of the 5000 CB CD34⁺ cells. The results are expressed as mean ± standard deviation. Data represent 8 independent experiments, each done in quadruplicate.