OBJECTIVETo develop an easy method to amplify natural killer (NK) cells by using mononuclear cells in vitro, so as to lay the basis for NK cell therapy.

METHODSUmbilical cord blood from 3 healthy full-term pregnant women was collected, and the peripheral blood mononuclear cells (PBMNC) were harvested by density gradient centrifugation. Each sample of PBMNC was divided into 3 groups: CD16mAb, CD3 mAb and CD16mAb+CD3mAb- groups. The culture flasks were pre-coated with CD16, CD3 or CD3 plus CD16 mAb. The PBMNCs were cultured in serum-free media containing autologous plasma, recombinant human IL-2, IL-15 and IL-21 for 14 days under the same conditions. The total viable cell count was calculated. Flow cytometry was used to determine the ratio of CD56CD3 cells, MTT assay was used to measure the killing rate of NK cells under different effector/target ratio, by using the K562 cells as the target cells.

RESULTSAfter 14 days of culture, the total cell numbers of CD16mAb, CD3mAb and CD16mAb +CD3mAb groups increased by 45.71±5.54, 87.41±19.77 and 4.88±51.84 times, respectively, and those of CD3mAb group were significantly higher than the other 2 groups (P<0.05). The ratio of CD56CD3 cells before culture was 0.1663±0.0201, which was 0.8167±0.0500, 0.8077±0.0589 and 0.8077±0.0273 after incubation with CD16mAb, CD3mAb and CD16mAb +CD3mAb for 14 days, respectively (P>0.05). MTT test showed that the killing efficiencies were not significantly different among the 3 groups when the effector/target ratios were 1:1, 5:1 and 10:1 (P>0.05).

CONCLUSIONBy incubation with anti-CD3 monoclonal antibody, IL-2, IL-15 and IL-21, the highly purified NK cells can be obtained from mononucleated cells, thus providing a simple method for NK cell therapy.