Dendritic cell maturation by CD11c- T cells and Vα24+ natural killer T-cell activation by α-galactosylceramide

Human invariant V alpha 24(+) natural killer T (NKT) cells display potent antitumor activity upon stimulation. Activation of endogenous V alpha 24(+) NKT cells would be one strategy for the treatment of cancer patients. For example, dendritic cells (DCs) loaded with a glycolipid NKT cell ligand, alpha-galactosylceramide (alpha GalCer, KRN7000), are a possible tool for the activation and expansion of functional V alpha 24(+) NKT cells in vivo. In this report, we demonstrate that the levels of expansion and the ability to produce IFN-gamma of V alpha 24(+) NKT cells induced by alpha GalCer-loaded whole PBMCs cultured with IL-2 and GM-CSF (IL-2/GM-CSF-cultured PBMCs) were superior to those of cells induced by monocyte-derived CD11c(+) DCs (moDCs) developed with IL-4 and GM-CSF. Interestingly, CD11c(+) cells in the IL-2/GM-CSF-cultured PBMCs showed a mature phenotype without further stimulation and exerted potent stimulatory activity on V alpha 24(+) NKT cells to enable them to produce IFN-gamma preferentially at an extent equivalent to mature moDCs induced by stimulation with LPS or a cytokine cocktail. Cocultivation with CD11c(-) cells in the IL-2/GM-CSF-cultured PBMCs induced maturation of moDCs. In particular, CD11c(-)CD3(+) T cells appeared to play important roles in DC maturation. In addition, TNF-alpha was preferentially produced by CD11c(-)CD3(+) T cells in IL-2/GM-CSF-cultured PBMCs and was involved in the maturation of moDCs. Thus, the maturation of DCs induced by CD11c(-) T cells through TNF-alpha production appears to result in the efficient expansion and activation of V alpha 24(+) NKT cells to produce IFN-gamma preferentially. (c) 2005 Wiley-Liss, Inc.