Infection of K562 cells with influenza a virus increases their susceptibility to natural killer lysis

Natural killer (NK) cells play a role in the natural immunity against tumor cells. In the present study, we demonstrate that infection of the NK-sensitive tumor cell line K562 with influenza A virus caused a substantial increase in lysis of up to sevenfold when compared to noninfected cells. Similar to NK cells, IL-2-activated killer cells exhibited higher lytic activity against virus-infected K562 cells. This effect of the virus correlated with the increase in the expression of intracellular adhesion molecule-1 (ICAM-1) on K562 cells. Changes in the susceptibility to NK lysis were accompanied by alterations, within minutes, in the cytoskeleton as detected by intracellular fluorescein fluorescence polarization measured on the Cellscan, a static cytometer. The possible role of ICAM-1 and the cytoskeleton in the cytotoxic response of NK cells is discussed.