Rest your cells out of growth factor for 24hr and then stimulate with a combination of IL-12 and IL-18.

You can use monoclonal antibodies against NKG2D and NKG2C to activate the cells. Nkp30, 44 and 46 can also trigger NK cell cytotoxicity.

Thanks for suggestion. I used the NKG2D and NKp30 to activate my NK92-MI cells (also compare with its isotype control) at 1ug/mL concentration for overnight stimulation. The next day I perform a co-culture with the K562 cells and I ran the 96 CytoTox assay, and I did not see any upregulation of 'killing" with the activated call compare to the naïve NK-92 cells. Is the concentration I am using too low or my time point too short? Please advise