Monocytes and DCs differ in their survival mechanisms.

(A) DCs were cultured in RPMI-10% FCS with the addition of IL-4 and GM-CSF, whereas freshly isolated peripheral blood monocytes were cultured in RPMI-10% FCS alone. After 48 hours of culture, the effects of GM-CSF deprivation (No GM-CSF) or treatment with PD98059 (50 μM), SB203580 (10 μM), LY294002 (20 μM), Rapa (1 μM), or DMSO, were analyzed using Hoechst. Results demonstrate mean ± SD percentage of apoptosis of 3 independent experiments with different donors. * indicates significant apoptotic effect of “No GM-CSF” compared with “GM-CSF” or an inhibitor compared with its solvent “DMSO” (P < .05; Student t test for paired samples). (B) DCs were cultured with IL-4 and GM-CSF in the presence of various concentrations of the PI3K-inhibitor LY294002, or DMSO. Cells were analyzed after 24 hours or 48 hours using Hoechst (n = 2). (C) Day-6 DCs were harvested, extensively washed, and further cultured in RPMI-10% FCS supplemented with IL-4 plus GM-CSF (control), IL-4 alone (No GM-CSF), or IL-4 plus GM-CSF with either Rapa (1 μM), LY294002 (20 μM), PD98059 (50 μM), or SB203580 (10 μM) added. After 48 hours, ΔΨ_m was investigated using Rh123. The percentage of cells with a decreased ΔΨ_m are plotted in a histogram. Data are shown as the mean ± SD percentage of apoptosis of duplicate cultures, representative for 3 to 6 independent experiments with different donors. * indicates significant apoptotic effect compared with “GM-CSF” or “DMSO” (P < .05; Student t test for paired samples).