Inhibition of CD34⁺ cell differentiation into DC is mediated by IL-6 and M-CSF. These results are expressed as the percentage of CD14⁺ and CD1a⁺ cells. CD34⁺ cells were cultured with GM-CSF+TNF alone () or in the presence of 10% CLB-VER CM (▨) from day 6 to 12. Neutralizing antibodies were added alone or in combination at 10 μg/mL. At day 12, cells were harvested and processed for double labeling with CD14-PE and CD1a-FITC. For all conditions, the SD ranged from 1% to 2%. *P < .01 as compared with RCC CM-treated cells.