Figure 4. The proliferation of naïve CD4⁺ and CD8⁺ cells after vaccination with Ag-loaded DCs is inhibited by WT, but not PKO, CTLs. (A-C) WT and PKO CTLs were generated as described in the legend to Figure 1 and transferred i.v. into syngeneic recipients together with CD45-congenic, CFSE-labeled naïve T cells. One day later, mice were vaccinated with Ag-loaded DCs or DCs only. Proliferation of the naïve T-cell population was assessed in draining LNs 3 d after vaccination. (A) Representative flow plots of naive L318 CD8⁺ T cells recovered from the draining LNs of mice adoptively transferred with L318 CTLs and immunized with DCs. (B) Percent naïve L318 CD8⁺ T cells divided 5 times or more, recovered from the draining LNs of the indicated experimental groups. Data are from one of two experiments that gave similar results and are from the same experiment shown in (A). Each symbol corresponds to one mouse. (C) Numbers of divided, naïve OT-I CD8⁺ T cells and OT-II CD4⁺ T cells recovered from the draining LNs of mice that were adoptively transferred with 5 × 10⁶ WT or PKO OT-I CTLs, and immunized with 0.5 × 10⁶ WT or Faslpr DCs. Bar graphs show means + SEM for groups of 4–10 mice. NS: not significant; *: 0.01 < p < 0.05; **: 0.001 < p < 0.01; ***: p < 0.001 by one-way ANOVA with Tukey’s post-test.