Fas ligation at the time of activation accelerates cell division and IFN-γ production in the surviving cells.

Naive OT-II T cells were activated in coculture with dendritic cells pulsed with 2 mg/mL OVA. (A) Cell division was determined at day 3 (left panels) and day 6 (right panels). Upper panels: cells costimulated with anti-Fas (open histograms) or control antibody (shaded histograms). Lower panels: cells costimulated with cross-linked FasL (open histograms) or anti-FLAG (shaded histograms). OT-II T cells were CFSE-labeled prior to coculture. A representative staining from 1 of 3 separate experiments for each panel is shown. Cells were stained with phycoerythrin-conjugated anti-CD4 and 7-AAD. Events were gated for viable (7-AAD⁻) CD4 T cells. (B) IFN-γ production in cocultures of naive OT-II T cells and DCs. DCs were pulsed with 2 mg/mL ovalbumin, and either control (■) or anti-Fas (a-Fas) (▪) or anti-FLAG (a-FLAG) (▥) mAb or FasL (▤) was added at the start of coculture. IFN-γ concentration was determined from supernatants at day 5 using specific ELISA. Results are the mean ± SEM of 3 individual experiments. P values were calculated using the Student t test.