The effect of 30 μM ebselen or 7.5 mM NAC on the levels of oxidative DNA damage in the 400–23 CD4+TCC when supplemented from a young in vitro age or when supplemented from a later stage in the lifespan. A &C illustrates the effect of 30 μM ebselen and B &D illustrates the effect of 7.5 mM NAC. The bars indicate the mean ± S.D. Values statistically different from their controls (Student’s t-test, 95% confidence level) are indicated with an asterisk. * p < 0.05, ** p < 0.01, *** p < 0.001 - Significantly higher than the levels of DNA damage in non-supplemented cells.