Human polymorphonuclear leukocytes (PMN) and granule-free cytoplasts were compared for their cytotoxic capacities against red blood cells (RBC) and K562
tumor cells.
Phorbol myristate acetate (PMA) stimulated PMN to efficient lysis of RBC targets, while cytotoxicity against the tumor cell line K562 was moderate. Activated cytoplasts also lysed RBC targets but were not able to kill K562
tumor cells, even at high cell numbers. Suppression of the
glutathione redox cycle of the K562
tumor targets markedly increased their susceptibility to lysis by PMA-activated PMN. Despite the enhanced susceptibility of
antioxidant-depleted K562
tumor cells to
oxygen radical-induced damage, PMA-stimulated cytoplasts did not kill these targets. Addition of exogenous
myeloperoxidase or
lactoferrin to cytoplasts devoid of granule did not improve the lysis of RBC and K562
tumor cells. Coating K562 targets with specific
antibodies induced efficient PMN-mediated killing in comparison to PMA-stimulated lysis of non-coated targets. Cytoplasts, however, did not kill antibody-coated K562
tumor cells; this was not improved by
glutathione depletion but showed some lysis of antibody-coated RBC. PMN from a patient with
chronic granulomatous disease (CGD) showed normal antibody-dependent cell-mediated cytotoxicity (ADCC) against K562
tumor cells but were not able to lyse these targets after PMA stimulation. The analysis of target cell killing by cytoplasts and PMN from a CGD patient indicated that granular constituents are important mediators in the killing of nucleated target cells and that PMN-mediated ADCC does not require the release of
reactive oxygen species. Differences in the susceptibility of target cells to
oxygen-mediated lysis indicates that target cell
antioxidant mechanisms play an important role in the outcome of the cytotoxic response.