Hi everyone,

I am struggling with expansion of human NK cells. NK cells are isolated from fresh PBMC by EasySep isolation kit with good yield (90-95%). After 5 days in culture in RPMI-1640 (10% FBS) with 100 IU/mL of hIL-2, there is around 50-70% of dead cells (SytoxBlue). I usually seed NK cells in conc. of. 1x10^6 cells/mL (24well) and replace media every 4-5th day. I tried 3 different hIL-2 and various conc (200IU-50IU/mL), but the results were the same.

I would like to use NK cells to check their cytotoxicity against K562 after preincubation of NK cells with some compounds.

Does anyone has any suggestion what I am doing wrong or how to improve the expansion/survival? If someone could share protocol for expansion I would be more than grateful.