ABSTRACT
We have previously reported that antioxidants such as beta-carotene, were able to enhance cytolytic activity of NK cells. The aim of the present study was to investigate whether preincubating YAC-1 tumor cells in culture with different antioxidants, affected their NK cell-mediated cytolysis. The antioxidants studied were enzymes (superoxide dismutase and catalase), hydroxyl radical scavengers (thiourea, mannitol, dimethyl sulfoxide) and a singlet oxygen quencher: beta-carotene. After 24 hours coincubation with the antioxidants, radiolabeled YAC-1 cells were submitted to the cytotoxic activity of NK cells for a 4 hour period. For some antioxidants, a moderate increase of cytotoxic potential occurred for weak NK cell number. By contrast, a clear decrease of cytotoxic potential was induced with high NK cell number. An antioxidant, with a protective effect which appeared stronger was thiourea, which induced 20, 58 and 36% decrease of cytolysis in the effector-target ratios 50:1, 100:1 and 200:1 respectively. These studies suggest that the malignant YAC-1 cells are vulnerable to treatment by different antioxidants.
