Conclusion
In UCB samples, alphaGalCer-pulsed DCs and NKT cells acted together to enhance NK cytotoxicity in vitro.
Methods
Mononuclear cells (MNCs) from UCB were cultured for 2 weeks in the presence of IL-2 (100 U/ml), with or without alphaGalCer. The effect of neutralizing monoclonal antibodies (MoAb) against TCRValpha24 and CD1d was also examined. TCRValpha24 Vbeta11 double positive NKT cells were purified by FACS sorter and then cocultured with syngeneic isolated UCB(-)CD56(+)NK cells in either the presence or absence of DCs. The cytotoxicity against various malignant cell targets and cytokine production was determined.
Purpose
The first objective of this study was to investigate in vitro effects of alpha-galactosylceramide (alphaGalCer) on the proliferation of umbilical cord blood (UCB) natural killer T (NKT) cells and enhancement of their cytotoxicity. The second one is to examine whether purified NKT cells could affect the cytotoxicity of UCB-NK cells either in the presence or absence of dendritic cells (DCs).
Results
The addition of alphaGalCer induced human NKT cells to proliferate in UCB-MNCs to a greater extent than in adult PB-MNCs. However, it suppressed the cytotoxic activity against malignant cell targets. Anti-TCRValpha24 and CD1d MoAb recovered the cytotoxicity by inhibiting the proliferation of UCB-NKT cells. NKT cells cocultured with auto-DCs significantly increased NK cell cytotoxicity against K562, and Raji cells and produced IFN-gamma at much higher levels than UCB-NKT cells alone.