Novel IL-15 dendritic cells have a potent immunomodulatory effect in immunotherapy of multiple myeloma

•Culture DCs with GM-CSF + IL-4 + IL-15 (IL-15 DCs) can be shortened for 6 days.•IL-15 DCs showed high expression levels of costimulatory receptors, IFN-γ and IL-12p70.•IL-15 DCs showed strong stimulation toward T, CIK and NK cells.•The activated lymphocytes showed high cytotoxicity against myeloma cells.