Inhibitory effect of IL-6 and M-CSF on APC function. CD34⁺ cells were cultured from day 6 to day 12 with GM-CSF+TNF alone (□) or in the presence of exogenous cytokines (▪) IL-6 (20 ng/mL), (▵) M-CSF (20 ng/mL), (○) VEGF (25 ng/mL), or (•) Caki-1 CM (10%) alone. Cells generated were harvested at day 12, irradiated (30 Gy), and used as stimulator cells (17 to 10⁴ cells) in an allogeneic MLR with CD45RA⁺naive T cells (2 × 10⁴ cells/well) as described above. Results are representative of five experiments.