Effect of antioxidants on spontaneous eosinophil apoptosis in vitro. Eosinophils were incubated with control medium, GSH, NAC, DMSO, or TAUR for 19 hours (○) and 42 hours (•) at the concentrations indicated. Data are presented as mean ± SEM of 8 separate experiments. GSH (optimal concentration, 5 to 10 mmol/L) more than NAC (optimal concentration, 10 mmol/L) inhibited spontaneous eosinophil apoptosis. In contrast, higher concentrations of NAC and GSH (20 mmol/L) and DMSO (>1%) significantly induced eosinophil apoptosis. With TAUR, only 5 mg/mL significantly inhibited spontaneous eosinophil apoptosis after 19 hours, but this effect was not confirmed after incubation for 42 hours and was not dose-dependent. *P < .05, **P < .01, ***P < .001 versus unstimulated control. n.s., not significant.