Protective effect of IL-12 on tumor-derived supernatant (TDSN)-induced apoptosis. (a)Expression of HLA-DR and co-stimulatory molecules (CD40, CD80, CD83 and CD86) as well as secretion of cytokines (tumor necrosis factor (TNF)-α, IL-10 and IL-12) was determined for blood DCs following stimulation (24 h) with a cytokine cocktail (CC), synthetic double-stranded RNA (poly I:C) or CD40 ligand (CD40L) as described in Materials and methods. Histograms indicate expression in the absence (shaded) or presence (non-shaded) of stimulation. Numbers indicate delta mean fluorescence intensity (ΔMFI, stimulated cells minus unstimulated cells) and are representative of five independent experiments. (b)TDSN-induced apoptosis in blood DCs was determined by Annexin-V binding following incubation (24 h) in the presence or absence of exogenous IL-12 prior to culture (24 h) with 50% (v/v) peripheral blood mononuclear cell-conditioned supernatant (PBMC-SN) or TDSN (MA11, MB435, MCF7 and SKBR3). Representative dot plots (SSC on y-axis versus apoptosis on x-axis) are shown with numbers indicating the percentage of apoptotic cells. Five independent experiments were performed for which the p-value is indicated.