OBJECTIVETo establish a novel method for ex vivo expansion of natural killer cells from human umbilical blood, so as to provide the basis for NK cell therapy.

METHODSMononucleated cells from human umbilical blood were harvested and suspended in a serum-free medium containing 5% autologous plasma, recombinant human IL-15 (50 ng/ml) and hydrocortisone sodium succinate (5×10 mol/L) at a concentration of 1.5×10/ml, then the cells were seeded into flasks pre-coated with heparin sodium (100 U/cm) or/and anti-human CD16 antibody (1 µg/cm). After culture for 2 weeks, the cells were harvested and counted. Ratios of CD3/CD56 of the cells were determined by flow cytometry. MTT test was performed to assess the cytotoxicity against K562 cells with graded ratios of effector/target cells.

RESULTSIn contrast to the cells in flasks without pre-coating, the attached colonies appeared predominantly within 1 week of culture from heparin- and antibody-coated groups. The cell numbers from the pre-coated groups were significantly higher than that of uncoated one after culture for 2 weeks. Furthermore, the ratios of CD3/CD56 cells were much higher in pre-coated groups, and that of the cells from flasks pre-coated with heparin and antibody were the highest (all the P values <0.01). MTT test showed that the cytotoxic activity of the cells stimulated by precoating were much more potent than that of the cells without the stimulation.

CONCLUSIONAdvantageous expansion of NK cells can be achieved by precoating with heparin and anti-CD16 antibody, and also by supplement with IL-15 and hydrocortisone into the media, so the umbilical NK cells with high purity and potent cytotoxicity can be obtained.