Th1-polarizing capacity of clinical-grade dendritic cells is triggered by Ribomunyl but is compromised by PGE2: the importance of maturation cocktails.

The maturation state of (monocyte-derived) dendritic cells (DCs) determines the type of T-cell response. Currently, several maturation cocktails are used in clinical trials, most commonly a cocktail of TNF-alpha, PGE2, IL-1beta, and IL-6. The authors studied DC phenotype and functional ability to stimulate TH1 responses after maturation with different cocktails employing clinically approved agents. DCs were stimulated with the microbial agent Ribomunyl combined with IFN-gamma and various inflammatory cytokine cocktails: TNF-alpha/IL-1beta/IFN-gamma and TNF-alpha/PGE2 combined with monocyte-conditioned medium (MCM) or IL-1beta/IL-6. Regardless of the maturation cocktail used, all DCs possessed the characteristic phenotype of mature, migratory DCs (high expression of CD40, CD80, CD83, CD86, CCR7, MHC class I and MHC class II). Ribomunyl/IFN-gamma matured DCs produced high IL-12p70 levels, whereas other maturation stimuli did not. Even more striking, restimulation of Ribomunyl IFN-gamma mDCs with CD40-activating antibody reactivated IL-12p70 production. No IL-12p70 could be detected when DCs were stimulated with TNF-alpha/PGE2 combined with MCM or IL-1beta/IL-6, presumably by suppression by PGE2. Restimulation of these DCs with CD40-activating antibody failed to activate IL-12p70 production. Moreover, low levels of IL-10 were observed, possibly indicating inhibition of TH1-cell responses. Indeed, T cells stimulated with these DCs produced high levels of type 2 cytokine IL-5 and outgrowth of CD4CD25 T cells. This study shows that DC maturation with cytokine cocktails different from those most commonly used could be beneficial for immunotherapy trials in cancer patients.