IL-7 does not affect T-cell activation in vitro. (A) Total lymph node cells from F5 Rag1^−/− mice were cultured (10⁶/mL) with 10 nM NP68 in the presence or absence of IL-7 (10 ng/mL). Histograms are of pZap70 and CD69 levels on CD8-gated T cells in unstimulated (gray fill) or NP68-stimulated cultures with (solid line) or without (broken line) IL-7 for the times indicated. pSTAT5 staining is shown for IL-7–stimulated cells cultured with (solid line) or without (broken line) NP68 peptide compared with unstimulated cultures lacking IL-7 and NP68 (gray fill). (B,C) Total F5 lymph node cells were labeled with CFSE and cultured (10⁶/mL) with a range of peptide doses. At day 3, CFSE profile of viable CD8⁺ T cells was analyzed by FACS. Graphs show the percentage cells triggered into division (B) and mean division of triggered cells (C) in response to different doses of agonist NP68 peptide (circles) or the weak agonist NP34 (diamonds) in the absence (empty symbols) or presence (filled symbols) of IL-7 (10 ng/mL). (D) Histograms show expression of IL-7R, TCR, and CD8 by IL-7R⁺ F5 T cells from control (solid line) and IL-7R⁻ F5 T cells from F5 TetIL-7R mice off doxycycline for 7 days (gray fill). Histogram of IL-7R by CD4⁺CD8⁺ DP F5 thymocytes (broken line) is shown as negative control. (E) The graph shows CD69 expression at 18 hours by IL-7R⁺ F5 splenocytes of control mice (●) and CD8⁺ IL-7R⁻ F5 splenocytes from F5 TetIL-7R mice off doxycycline for 7 days (○), stimulated with different doses of NP68 peptide. Data are representative of 3 or more experiments.