Antigen-expressing DC inactivate long-lived memory CD8⁺ T cells. FACS-sorted CD45.1⁺ OT-I memory T cells (CD8⁺/CD44^hi) were transferred to 11c.OVA or nontransgenic (non-tg) mice. (A) The total number of OT-I (CD45.1⁺/CD8⁺/Vα2⁺) T cells in spleens of 11c.OVA (▴) or non-tg (□) recipients was determined at 3, 7, 14, 28, and 42 days after transfer. Data (mean±SD) are pooled from 2 independent experiments of 2 mice per group at each time point. Error bars represent SD. (B,C) Thirty-five days after OT-I transfer, mice were challenged with OVA/QuilA s.c or left unchallenged, and 7 days later (B), the total number of OT-I (CD45.1⁺/CD8⁺/Vα2⁺) T cells in spleens was determined (C) or the frequency of OT-I cells secreting IFN-γ in response to OVA_257–264 was determined by ELISpot assay. Data are pooled from 2 independent experiments with 2 mice per group. Horizontal bars represent mean values. (D) Thirty-five days after OT-I transfer, mice were challenged with OVA/QuilA s.c. or left unchallenged, and 7 days later, cytokine production by OT-I (CD45.1⁺/CD8⁺) cells was determined using ICS. Data are representative of 2 mice in each of 2 independent experiments. Numbers on plots are the percentages of cells in each quadrant (gated for CD8⁺, CD45.1⁺ cells).