CD86 and IL-12p70 Are Key Players for T Helper 1 Polarization and Natural Killer Cell Activation by Toll-Like Receptor-Induced Dendritic Cells

Background: Dendritic cells (DCs) determine the activation and polarization of T cells via expression of costimulatory molecules and secretion of cytokines. The function of DCs derived from monocytes ex vivo strongly depends on the composition of the maturation cocktail used. Methodology/Principal Findings: We analyzed the effect of costimulatory molecule expression and cytokine secretion by DCs on T and natural killer (NK) cell activation by conducting a head-to-head comparison of a Toll-like receptor (TLR) agonist-based cocktail with the standard combination of proinflammatory cytokines or IL-10 alone. We could show that TLR-induced DCs are characterized by a predominance of costimulatory over coinhibitory molecules and by high secretion of IL-12p70, but not IL-10. Functionally, these signals translated into an increase in IFN-gamma secreting Th1 cells and a decrease in regulatory T cells. T cell activation and polarization were dependent on IL-12p70 and CD86, but remarkably not on CD80 signaling. By means of IL-12p70 secretion, only TLR-induced DCs activated NK cells. Conclusions/Significance: TLR-matured DCs are highly suitable for application in immunotherapeutic strategies that rely on strong type 1 polarization and NK cell activation. Their effects particularly depend on high CD86 expression and IL-12p70 secretion.