Inhibition of antigen-presenting cell function by RCC CM. CD34⁺ cells were cultured from day 0 to 6 in GM-CSF+TNF. Medium was then changed and the cells were cultured in the presence of cytokine alone (control; □), RCC CM ([▪] CLB-VER CM; [○] Caki-1 CM), or breast CM (T47-D CM; •) from day 6 to 12. Cells were then harvested, irradiated (30 Gy), and used as stimulator cells for naive T cells (2 × 10⁴ cells/well). The proliferation was evaluated using ³HTdR uptake after 5 days of culture. Results are expressed as the mean ± SD of triplicate culture. These results are representative of five different experiments.