A FLOW CYTOMETRIC STUDY OF THE MEMBRANE-POTENTIAL OF NATURAL-KILLER AND K562 CELLS DURING THE CYTOTOXIC PROCESS

This study demonstrates that it is possible to investigate the membran e potential of interacting cells during the cytotoxic process using fl ow cytometry. Changes in the membrane potential of NK and K562 cells, involved in a cell-mediated cytotoxic process, were studied by standar d and slit-scan flow cytometry, using the membrane potential sensitive fluorescent probe DiBAC4(3). The NK cells were labeled with a membran e marker (TR-18 or DiI) prior to incubation with K562 cells and the co njugates that were formed could be identified on the basis of the memb rane marker fluorescence and light scattering signals. With a slit-sca n technique we measured the membrane potential of each cell in a conju gate separately. The results show that depolarization of the K562 cell occurs as a consequence of the cytotoxic activity of the NK cell. Thi s depolarization appears to be an early sign of cell damage because th e cell membrane still remains impermeable to propidium iodide. Our dat a also indicate that depolarization of the NK cell occurs as a result of its cytotoxic activity.