Selectively and Efficiently Expanding Natural Killer Cells in Vitro

Natural killer (NK) cells are the main innate immune cells, and have powerful antitumor activity in vitro, but NK cells based immunotherapy does not often get satisfactory results in clinical practice due to insufficient number and poor activity of NK cells.. Therefore, how to improve expansion efficiency and killing activity of NK cells in vitro is critical. Here we report an in vitro culture system culturing peripheral blood mononuclear cells (PBMC) with irradiated LCL as feeder cells in 10%FBS/RPMI1640 culture medium in the presence of 100U/ml IL-2 and 5ng/ml IL-15 for 14 days could selectively expand NK cells. With this culture system, the purity of NK cells increased from 11.5%± 7.01% to 75.3±10.9% (P< 0.01), and the expansion efficiency was about 625±63 times than the original PBMC. Compared with the fresh NK cells isolated from PBMC, there was no significant change in the expression of inhibitory receptors on the surface of expanded NK cells, while the expression of activating receptors was significantly increased (p<0.05). The cytotoxicity of expanded NK cells against leukemia cell line K562 was significantly higher than that of freshly isolated NK cells (72± 5.6% vs 8.7±2.3%, E: T=1, P<0.01), expanded NK cells also showed stronger cytotoxicity to LCL (22±3.6%, E: T=1) and primary leukemia cells (42±5.2%, E:T=1). In summary, we could selectively expand NK cells with this in vitro culture system, the expanded NK cells gained higher expression of NCRs and NKG2D receptors, and displayed greater cytotoxicity against tumor cells, therefore could be readily applied to anti-tumor treatment in clinical treatment. Figure Disclosures No relevant conflicts of interest to declare.