Inactivation of natural killer cell cytotoxic activity after interaction with target cells

Human peripheral blood lymphocytes were cultured with unlabeled target cells or absorbed to K562 cells and then isolated by centrifugation on discontinuous Ficoll-Methrizoate gradient. In both cases, lymphocytes that reacted with these target cells at 37 degrees C were inactivated and were no longer able to kill freshly added 51Cr-labeled target cells that were susceptible to spontaneous killing. This inactivation was time and temperature dependent and did not alter the ability of lymphocytes to lyse antibody-sensitized target cells. The natural killer (NK) cell inactivation that followed the interaction with target cells was not observed when target cells were used that were able to induce interferon (IFN) production when cultured with lymphocytes. This NK inactivation was reversed by incubation of the inactivated effector cell preparations with IFN.