CD40L, IFN-γ, and LPS have synergistic effects on IL-12 p40 and p70 secretion by monocyte-derived dendritic cells.

(A) 24-hour culture supernatants from DCs treated with several maturation agents, including the combination of CD40L and IFN-γ, were examined by ELISA specific for IL-12 p70. The graph shows the mean of triplicate values ± SD. Incubation of cells in medium alone, or with IFN-γ or TNF-α alone, resulted in the production of less than 1 pg/mL IL-12 p70. Data are representative of 2 experiments in different donors. (B) After sampling of culture supernatants for ELISA, brefeldin A was added, and the incubation was continued for another 4 hours. Cells were then harvested, fixed, permeabilized, and stained with α-CD11c-FITC, α-CD14-PerCP, and α-IL-12(p40/p70)-PE. 25 000 large, CD11c⁺/CD14⁻ cells were analyzed by flow cytometry and are represented in the scatter diagrams shown. The indicated percentage represents the frequency of IL-12⁺cells. R3 denotes the region containing IL-12⁺ DCs. Data are representative of 5 experiments with similar results.