Expansion of human natural killer cells ex vivo

AIM: To obtain sufficient numbers of pure and activated human primary NK cells for potential clinical application. METHODS: PBMC based ex vivo expansion of natural killer cells was set up. The expansion was initiated by co-culture of PBMC and stimulator cells (irradiate genetic modified K562 cells) in RPMI1640 medium with 1 000 U/mL IL-2. Genetic modified K562 cells 'K562D3' were prepared by expressing IL-15, 4-1BBL and IL-18 on K562 cell membrane. RESULTS: An average of 500 fold expansion of CD56(+)CD3(-) cells was observed after 3 weeks of co-culture. The NK cells population could reach 93% after expansion, comparing with 7% before expansion. The expanded NK cells lysed 95% of K562 targets in a 5:1 effector to target ratio. IL-15/4-1BBL bound K562 stimulatory cells could expand same fold NK cells as K562D3, but the cytotoxicity of NK cells expanded by 'K562D3' was 10% higher. CONCLUSION: The described method is a simple and efficient way for the expansion of human NK cells.