CD8⁺ T cells proliferating in response to alloantigen are selectively killed by LPR DN T cells via the Fas pathway.

<p>CD8⁺ T cells (10⁵/well) from B6 (Fas^+/+) or B6.LPR (Fas^LPR/LPR) were labelled with CFSE and cocultured with irradiated CB6F1 splenocytes and IL-2 for 5 days without or with LPR DN T cells in the indicated ratios. After 5 days, the cultures were stained with anti-CD8-APC and 7-AAD and analyzed by flow cytometry. <b>A.</b> The percentage of undivided cells (CFSE^hi) was used to determine the percent suppression at each DN:CD8⁺ T cell ratio. Two-way ANOVA p<0.0001 for the effect of CD8⁺ T cell Fas expression. <b>B.</b> Representative histograms of 7-AAD staining gated on proliferated (CFSE-diluted) Fas^+/+ (top row) and Fas^LPR/LPR (bottom row) CD8⁺ T cells at the indicated DN:CD8⁺ ratios. Numbers inside histograms are the percentages of cells falling in the 7-AAD⁺ gate. <b>C.</b> The fold increase in cell death for proliferated Fas^+/+ (white bars), proliferated Fas^LPR/LPR (black bars), unproliferated Fas^+/+ (light grey bars), proliferated Fas^LPR/LPR (dark grey bars) CD8⁺ T cells is shown. Two-way ANOVA p<0.0001; Bonferrroni post-tests ***p<0.001 and *p<0.05. Data are derived from two independent experiments each with duplicate wells.