The Generation of Potent Dendritic Cells Can Be Modulated by Interaction between Immature Dendritic Cells and Invariant NK Cells with the Presence of Stimulatory Cytokines and TLR Agonist.

For the therapeutic DC-based immunotherapy, peripheral blood derived-monocytes are cultured with the presence of exogenous GM-CSF and IL-4 by in vitro amplification. However, the different cells of the innate and adaptive immune system interact with each other and affect the activation and maturation of DCs for subsequent T-cell priming in vivo. We investigated what kind way of cultivation was more effective for the induction of mature DCs (mDCs) in vitro, compared the coculture with invariant NK cells and iDCs under the stimulatory molecules to the coculture with iDCs added to the activated NK cells stimulated by same molecules.

Experimental Methods: To evaluate the NK-cell-mediated DC maturation, we divided two different combinations of the coculture of NK cells and iDCs. In the activated NK-cell-mediated DC maturation, isolated CD3-CD56+ NK cells were activated by IL-2 alone, combined IL-2 with TLR3 agonist (poly I:C) and combined IL-2 with TLR3 agonist and IFN-α. These activated NK cells were cocultured with iDCs and were differentiated into mDC. In the invariant NK-cell-mediated DC maturation, isolated CD3−CD56+ NK cells were cocultured with iDC, and then, the invariant NK cells and iDCs were stimulated simultaneously by same stimulatory methods. After harvesting the mDCs and their supernatants, the phenotype and functional capacities of mDCs were analyzed and IL-12p40 productions of mDCs were estimated by immunoassay.

Results: The expressions of several molecules on DCs and IL-12p40 productions by DCs were significantly higher under the stimulation of IL-2, TLR3 agonist and IFN-α than IL-2 alone or combined with IL-2 and TLR3 agonist in the invariant NK-cell-mediated DC maturation. However, the DC phenotypes and IL-12p40 productions in the activated NK-cell-mediated DC maturation did not show any differences to the same stimulatory methods. When comparing the functional capacities and IL-12p40 productions according to the way of the activated NK-cell-mediated and invariant NK-cell-mediated DC maturation, the functional capacities of DCs from the invariant NK-cell-mediated maturation were significantly higher than those of DC from the activated NK-cell-mediated maturation with the stimulation of IL-2, TLR3 agonist, and IFN-α. IL-12p40 productions were more improved from the invariant NK-cell-mediated maturation than the activated NK-cell-mediated maturation.

Conclusions: The invariant NK cells can promote the generation of DCs through the coculture with iDCs under the stimulation of IL-2, TLR3 agonist and IFN-α. However, the activated NK cells did not enhance the DC functions. This study emphasized the potential for manipulating the interaction between DC and NK cells in the generation of mDCs.

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