Saturating antigen-presenting capacity overcomes the triggering defect in IL-7R⁻ F5 T cells. (A) Control F5 T cells were CFSE-labeled and transferred to Rag1^−/− hosts (3 × 10⁶ cells/mouse), and groups of mice were challenged with a range of NP68 peptide doses at 0 and 18 hours after transfer. At day 3, mice were culled and the responding T-cell population analyzed by FACS. The scatter plot shows the percentage of control F5 T cells triggered into division in individual mice challenged with different doses of peptide. (B) F5 T cells from CD45.1⁺ control F5 (IL-7R⁺ F5) and CD45.1⁻ F5 TetIL-7R mice off doxycycline 7 days (IL-7R⁻ F5) were CFSE-labeled, mixed at a 1:1 ratio, and transferred (3 × 10⁶ total T cells/mouse) to groups of Rag1^−/− hosts challenged with a range of NP68 peptide doses. At day 3, mice were culled and CFSE profile of IL-7R⁺ F5 and IL-7R⁻ F5T cells analyzed by FACS. Scatter plot shows the percentage of F5 T cells triggered into division for IL-7R⁺ F5 (x-axis) versus IL-7R⁻ F5 (y-axis) T cells in the same recipient (B) and ratio of IL-7R⁻ F5: IL-7R⁺ F5 as a function of peptide dose (C). Data are representative 2 independent experiments.