SIINFEKL-specific but not spontaneous memory T cells are restimulated by cross-presenting APCs. (A-B) K^b−/− and actOVA. K^b−/− mice were irradiated and reconstituted with C3H.SW BM and 5 × 10⁵ sort-purified CD8⁺CD44⁺ CD8 cells from C3H.SW mice vaccinated 60 days earlier with anti–DEC205-OVA. Mice were killed 13 days after transplantation. (A) Representative flow cytometry (gating on Ly9.1⁺CD8⁺ cells). (B) Number of Tet^SIINFEKL+ cells per spleen. P = .024. (C) K^b−/− and actOVA.K^b−/− mice were transplanted as in panel A, except that they received C3H.SW sort-purified naive CD8⁺CD44⁻CD62L⁺ (1 × 10⁶) or memory CD8⁺CD44⁺ (3 × 10⁵) cells, with or without 10⁵ CD4⁺CD25⁻ cells. Representative flow cytometry of spleen, LN, and blood is shown in panel C (gated on Ly9.1⁺CD8⁺ cells). Percentage of CD8 cells that were Tet^SIINFEKL+ and total number of Tet^SIINFEKL+ per spleen are shown in panel D. P = .0043, comparing percentage and total number of Tet^SIINFEKL+ cells in recipients of CD4 cells and T_N versus CD4 cells and T_M. P < .036, comparing percentage and total number of Tet^SIINFEKL+ cells in recipients of T_N with or without CD4 cells. Data combined from 2 independent experiments.