ABSTRACT
<p><b>OBJECTIVE</b>To investigate the apoptosis of NK cells induced by the erythroleukemia cell line K562 in vitro.</p><p><b>METHODS</b>Primary NK cells isolated from the peripheral blood of healthy donors by magnetic-activated cell sorting were cultured with stem cell medium containing recombinant human interleukin-2 (rhIL-2). The NK cells and K562 cells were mixed and co-cultured at different E:T ratios for different time lengths. The apoptosis of NK cells and K562 cells were detected using PE-AnnexinV/7-AAD labeling and flow cytometry.</p><p><b>RESULTS</b>The purity of isolated NK cells reached (93.99∓4.22)%. At the same E: T ratio, the apoptotic rate of NK cells induced by K562 cells increased significantly with time. As the E:T ratio reduced, the apoptotic rate of the NK cells increased and their cytotoxic activity against K562 cells was attenuated.</p><p><b>CONCLUSION</b>K562 cells can induce the apoptosis of activated NK cells, which is one of the probable mechanisms of immune escape of tumors.</p>