Inhibition of dendritic cell-driven regulatory T cell activation and potentiation of tumor antigen-specific T cell responses by interleukin-15 and MAP kinase inhibitor

A method of preparing a therapeutic composition comprising antigen-specific T cells or dendritic cells loaded with an antigen, the method comprising:

• (1) culturing adherent peripheral blood mononuclear cell (PBMC) dendritic cell recursors ex vivo in the presence of GM-CSF, IL-4, IL-15 and a p38 MAP kinase inhibitor in amounts and for a time effective to differentiate said precursors into dendritic cells that function to reduce Treg activity and FoxP3 expression in T cells, and further comprising stimulating antigen-specific T cells ex vivo with said dendritic cells that have been loaded with an antigen;
• or
• (2) culturing adherent PBMC dendritic cell precursors ex vivo in the presence of GM-CSF, IL-4, IL-15 and a p38 MAP kinase inhibitor in amounts and for a time effective to differentiate said precursors into dendritic cells that function to reduce Treg activity and Foxp3 expression in T cells contacted with the dendritic cells, and loading the dendritic cells with an antigen ex vivo.