Effect of NAC on T cell–mediated cytotoxicity. (a) Cytotoxic activity of purified human PB T cells stimulated in the presence of NAC against HL60 cells in a resting state. In all the experiments, T cells were stimulated for 16 hours with PMA plus ionomycin in the presence of increasing concentrations of NAC and then washed before fixation with PFA. Cytotoxic assays were performed against HL60 cells at the effector to target cells ratio 1:1 (○) and 10:1 (▵). In some experiments performed with an effector to target cell ratio of 1:1, 20 mmol/L NAC were added in the medium during the cytotoxic assays (•). Results are expressed in percent of cytotoxicity (mean ± SD, n = 8). (b) Neutralization of the T cell–dependent cytotoxicity with anti-TNFα Abs. The cytotoxic assays were performed at the effector to target cell ratio of 1:1 with T cells stimulated without or with NAC in the absence (□) or the presence of two different neutralizing anti-TNFα Abs (▨ and ▪). Results are expressed in percent of inhibition of cytotoxicity (mean ± SD, n = 8). *Means P < .01. (c) Effect of NAC on lytic activity of antigen-specific mouse CTL. The effector CTL QB7.3.2 clone was pretreated (•) or not (○) with 20 mmol/L NAC during 3 to 12 hours and then washed but not fixed with PFA. 51Cr-labeled P815 target cells, pulsed with the peptide PbCS 252-260, were incubated with the pretreated CTL at the indicated effector to target cells ratio. Cytotoxic assays were performed in the absence of exogenous NAC. Results are from one out of three representative experiments.
