Involvement of intrinsic GSH in WI38 supernatant-promoted activated T-cell survival. (A) Activated T cells, deprived of IL-2, were incubated in the presence (•) and absence (○) of WI38-derived supernatant (50%). The GSH content of the cells was determined initially (day 0) and after culture for 1 and 2 days. Two further independent experiments gave similar results. (B) IL-2–deprived T cells were incubated for 2 days with (•) and without (○) WI38-derived supernatant (50%) in the presence of increasing concentrations of BSO. Values are means ± SEM of triplicate cultures. (C) WI38-derived supernatant was crudely fractionated using Amicon C30 ultrafiltration units (see Materials and Methods). This yielded fractions containing either low molecular weight proteins (<30 kD) or higher molecular weight proteins (<30 kD). IL-2–deprived T cells were incubated alone (C), with unfractionated supernatant (Sup; 50%) or with the appropriate fractions (<30 kD and <30 kD; 50%). The data shows the percentage survival at day 5 in a representative experiment, and the values are means ± SEM of triplicate cultures. Numbers in brackets show the total GSH content of the cells (nmol/10⁶ cells) as determined after a 2-day incubation. In two separate experiments, the GSH content after 5 days in the controls compared with the cultures to which W138 supernatants were added was 0.89 versus 1.87 nmol/10⁶ cells and 0.64 versus 1.51 nmol/10⁶ cells, respectively.