The effect of IL-7 on Fas-mediated T-cell costimulation. (A) T cells isolated from noninfected donors were cultured without any treatment (left panel) or in the presence of IL-7 (right panel) for 5 days. Thereafter, proliferation was triggered using 1 μg/mL anti-CD3 Abs combined with anti-Fas or control Abs. Thymidine incorporation was measured after 3 days of activation. Error bars represent standard deviation measured in triplicates; 1 representative experiment of 3 is shown. (B) T cells, freshly isolated or pretreated with 25 ng/mL IL-7 for 5 days, were activated with 1 μg/mL anti-CD3 Abs combined with anti-Fas or control Abs. IL-2 production was measured in culture supernatants using ELISA after 3 days of activation. One representative experiment of 3 is shown. (C) CD25 and CD69 expression was measured in freshly isolated or IL-7–pretreated T cells at baseline or after 3 days of activation using 1 μg/mL anti-CD3 in combination with anti-Fas or control mAbs. (D) Kinetics of CD25 expression is shown following activation of freshly isolated or IL-7–pretreated T cells using 1 μg/mL anti-CD3 combined with anti-Fas or control Abs. A representative result of 3 independent experiments is shown.