Figure 2.

PD-1 mediates CTL deletion in the RLN, but not in the spleen. (A) Experimental scheme for OT-I survival analysis. The 5×10⁶ CFSE-labeled OT-I (white) or OT-IxPD1^−/− (black) cells are transferred into wild-type recipients, which are then immunized with 8 µg/g body weight endotoxin-free OVA intravenously or OVA/CpG subcutaneously (pos ctrl; gray). One day later, single cell suspensions from RLN, spleen, or draining cutaneous LNs are analyzed for absolute OT-I cell numbers by flow cytometry. Suspensions are transferred into separate secondary recipient mice, and the proportion of transferred OT-I cells that survive (B) and produce IFN-γ (C) are determined in pooled spleen and LNs after 5 days. Data are representative of four independent experiments. CFSE, carboxyfluorescein succinimidyl ester.