Figure 4.

Endogenous Memory CD8⁺ T Cells Effectively Raise the Activation Threshold

(A and B) All mice received 10⁴ OT-1 T cells and some 3 × 10⁵ (A) or 10⁶ (B) memory P14 T cells. The OT-1 frequency among total CD8⁺ T cells was determined 7 days after infecting the mice with Lm-gp33-N4 or Lm-gp33-T4. Data are representative for two independent experiments with n = 5 mice per group.

(C–E) CD45.1 P14 memory T cells were obtained from mice infected 30–90 days earlier with LCMV and transferred into naive mice. Shown are memory P14 T cell populations before and after the transfer. Bars represent individual mice, and the relative distribution of the indicated P14 subsets. The plots on the right show the frequency of KLRG1⁺ (C) and CD27⁺CD43⁺ subpopulations (D). Dots represent individual mice.

(E) Mice with endogenous memory cells were i.v. injected with fluorescently labeled anti-CD8 antibody and sacrificed 3 min. later. CD127/KLRG1 and CD27/CD43 expression status on antibody-positive and -negative cells are shown as indicated in (D). Data are representative for two to four independent experiments with n = 3–5 mice per group. Statistical analyses are unpaired Student’s t tests with ^∗p < 0.1, ^∗∗∗p < 0.001, and ^∗∗∗∗p < 0.0001.