ABSTRACT
This study was purposed to investigate the amplification of CD3(-)CD56(+)NK cells in umbilical cord blood and their change of immunophenotype and cytotoxicity after stimulation with IL-2 and IL-15. Mononuclear cells were isolated from umbilical cord blood and cultured in serum-free medium supplemented with IL-2 or (and) IL-15 for 14 d. The subset level of CD3(-)CD56(+)NK cells and expression of CD16, CD62L, NKG2A, NKG2D, NCR44, NCR46, granzyme B and perforin were analyzed by flow cytometry. The cytotoxicity of NK cells to K562 was detected by WST-1 method. The results showed that NK cells stimulated with IL-2, IL-15 and IL-2/IL-15 were amplified by 10.78 ± 2.51, 10.42 ± 3.72, and 10.54 ± 6.24 times respectively after 14 d, there was no statistically significant difference between these three groups. The expression of CD16 decreased obviously in NK cells after amplification; there was significant difference between IL-2 and IL-15 groups. The expression of CD62L was not changed statistically after stimulation with cytokines, the IL-2 down-regulated the expressions of NKG2A and NCR46, while IL-15 showed the opposite effect. IL-2 or IL-15 displayed upregulation effect on the expression of NKG2D, perforin and NCR44, but there was statistically significant difference between effects of these two cytokines. IL-15 up-regulated the expression of granzyme B on NK cells. The cytotoxicity of NK cells stimulated and amplified by cytokines significantly increased, but there was no statistically significant difference between IL-2 and IL-15. It is concluded that IL-2 or IL-15 can effectively amplify umbilical cord blood NK cells under serum-free conditions. Although the immunophenotype associated with NK cells function showed different characteristics between them, however, cytotoxicity of NK cells increased obviously after amplification and there is no statistically significant difference between effect of these two cytokines, their synergistic effect is not obvious. The cytotoxicity of NK cells is the result from combined effect of all active molecules.