The effects of GalCer-induced TCRV24 V11 super(+) natural killer T cells on NK cell cytotoxicity in umbilical cord blood

Mononuclear cells (MNCs) from UCB were cultured for 2 weeks in the presence of IL-2 (100 U/ml), with or without GalCer. The effect of neutralizing monoclonal antibodies (MoAb) against TCRV24 and CD1d was also examined. TCRV 24 V11 double positive NKT cells were purified by FACS sorter and then cocultured with syngeneic isolated UCB super(-)CD56 super(+)NK cells in either the presence or absence of DCs. The cytotoxicity against various malignant cell targets and cytokine production was determined. The addition of GalCer 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-TCRV24 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- at much higher levels than UCB-NKT cells alone. In UCB samples, GalCer-pulsed DCs and NKT cells acted together to enhance NK cytotoxicity in vitro.