C57BL/6 mice containing donor Thy1.1+ OT-1 CD8+ T cells were treated daily with PBS, 0.01, 0.1, 1 or 10 μg of native SIINFEKL peptide between days 0-2. (a) Day 3 flow cytometric analysis of donor OT-1 cells in the spleen stained with antibody specific for indicated molecule. Lines; Shade – PBS, dashed – 0.1 μg, thin – 1 μg and thick – 10 μg treatments. (b) Day 3 ex vivo phosphorylation of Erk in OT-1 cells re-stimulated with SIINFEKL peptide (thin line) or unstimulated (dashed line). Treatment condition indicated in top right hand corner of plots and the mean MFI increase from unstimulated to stimulated cells in parenthesizes. (c) Survival of OT-1 cells in the spleen. Expressed as the percentage of OT-1 cells detected by FACS on day 6 compared to day 3 for each treatment condition. Each graph is representative of 2 to 3 independent experiments using age and sex matched mice.