Figure 3. WT and PKO CTLs respond equally well to Ag presented in the LN. (A) Naïve mice were injected s.c. with a 1:1 mix of CFSE-labeled Ag-loaded DCs, and CTO-labeled DCs with no Ag. Six h later, half of the mice were injected i.v. with OT-I CTLs activated in vitro as described in Figure 1. At the indicated time points, mice were sacrificed and the numbers of CFSE⁺ and CTO⁺ DCs in draining LNs were evaluated by flow cytometry. Each symbol shows mean ± SEM for a group of 3–6 mice; data are from one of two experiments that gave similar results. (B, C) WT and PKO L318 CTLs were generated as described, labeled with CFSE and transferred i.v. into CD45-congenic recipients that had been injected s.c. one day earlier with Ag-loaded DCs or DCs only. CTL responses were examined in draining LNs 66 h after CTL transfer. (B) Representative flow plots of live CD8⁺ cells recovered from the draining LNs of mice adoptively transferred with WT or PKO CTLs and immunized with DCs only or Ag-loaded DCs. Gates highlight large activated cells (top row) or divided cells (lower row). (C) Expansion of WT and PKO CTLs in draining LNs of mice vaccinated with DCs only or Ag-loaded DCs. Each dot represents one mouse, gating was as in (B). Combined data from two independent experiments are shown. NS: not significant.