WT1 peptide vaccination induces memory CD8⁺ T cells which are functional and WT1-specific. (A-D) Peripheral blood lymphocytes (PBLs) from C57BL/6 mice were isolated 28 days after the first vaccination. (A) Representative flow cytometry plots show percent of gated CD8 T cells staining positively for CD44 and WT1-tetramer (box) after 1 to 4 vaccinations. Plots are representative of 5 mice per group. (B) Mean percentage of CD8⁺ WT1-tetramer⁺ cells among gated CD8⁺ T cells (*P < .001). (C) Representative flow cytometry plots show percent of gated CD8⁺ T cells stained positively for CD44 and intracellular IFN-γ (box) after 24-hour coculture with irradiated FBL3 tumor cells or H11 tumor cells (negative control). Plots are representative of 5 mice per group. (D) Mean percentages of CD8⁺IFN-γ⁺ T cells among gated CD8⁺ T cells (*P < .001).