Exogenous VEGF and IL-6 inhibit induction and maturation of DCs. (A) DCs were induced from adherent healthy donor PBMCs by culturing in the presence of GM-CSF (1000 U/mL), IL-4 (10 ng/mL), and 10% AB serum (□), with VEGF (20 ng/mL, ▦) or IL-6 (20 ng/mL, ▪), and TNF-α (10 μg/mL) was then added for 3 days. Cell surface expression of CD14, CD1a, and CD83 on DCs was analyzed by flow cytometry. Results indicate the mean ± SD of percent-positive cells in 4 experiments. Statistically significant increased expression of CD14 (*,P = .02) and decreased expression of CD1a (**, P = .02) and CD83 (***, P = .046) were observed with addition of IL-6 or VEGF. (B) T cells (2 × 10⁵ cells/well) from healthy donor PBMCs were incubated for 5 days with irradiated (15 Gy) autologous DCs generated in media containing 10% AB serum, GM-CSF, and IL-4 (□) with VEGF (20 ng/mL, ▦) or IL-6 (20 ng/mL, ▪) at indicated T-DC ratios. ³[H]thymidine (1.0 μCi [0.037 MBq]) was added to each well for the last 12 hours of 5-day cultures. Cells were then harvested and radioactivity was counted. Results are representative of 3 experiments, and values indicate mean ± SD of triplicate wells. Statistically significant decreased stimulation of T cells was observed with addition of VEGF or IL-6 (*, P = .02). Mean cpm of T cells without stimulators was 424 and of DCs only was less than 100.