(A) Experimental design: Thy1.2⁺ hosts were subjected to 0 Gy or 5 Gy dose of WBI. At 28 days later, the number and phenotype of Ag-specific CD8⁺ T cells specific for GP_33-41, B8R_20-27, GAP_41-48, and OVA_257-264 were determined using pMHC class I tetramer-based enrichment from spleens. (B) Representative flow plots showing gating strategy used to detect Ag-specific CD8⁺ T cell precursors and (C) virtual memory phenotype (CD44^hiCD49^loLy6C⁺) from Ag-specific CD8⁺ T cell precursors in 0 Gy and 5 Gy mice. (D) Absolute number and (E) frequency of virtual memory phenotype of D^b-restricted GP_33-41– and GAP50_40-48–specific and K^b-restricted B8R_20-27– and OVA_257-264–specific CD8⁺ T cells. (F) Experimental design: 7.5 × 10⁵ naive P14 CD8⁺ T cells were adoptively transferred to Thy1.2⁺ naive hosts that had undergone 0 Gy or 5 Gy WBI 2 days prior. Longitudinal blood analysis was performed at indicated time points. (G) Number of endogenous (left) and P14 (right) virtual memory (T_VM) CD8⁺ T cells in 0 Gy and 5 Gy hosts at indicated time points after WBI. Data in A–E are from a single experiment, and F and G are representative of 2 independent experiments with n = 5–8 mice per group in each experiment. Statistical significance was determined by unpaired multiple t tests with Holm-Šídák multiple-comparison post hoc test or 2-way ANOVA with Bonferroni’s multiple comparisons post hoc test using GraphPad Prism. Graphs show the mean ± SEM with each symbol representing 1 mouse. Individual P values are noted on respective graphs or are summarized as follows: *P < 0.05, **P < 0.01, ***P < 0.001.