(A) Hosts were injected with S.epi (1 × 10⁵ CFU s.c.) 30, 28, and 25 days before receiving S.epi-monocolonized syngeneic skin grafts. Grafts were scored on a 4-point scale (see Figure 1D). (B) Endogenous S.epi-specific T cells in the skin and SDLNs 1 month after S.epi immunization. Gated on CD45.2⁺TCRβ⁺CD8⁺CD4^–CD44⁺ H2-M3:fMIIINA–PE⁺ (tetramer against S.epi-reactive T cells) events. Plots show fold change relative to unimmunized mice (mean ± SEM) analyzed by Wilcoxon’s log-rank test. (C) Graft scores of syngeneic hosts with or without anti-S.epi memory that received GF or S.epi-monocolonized skin grafts (green line is also shown in Figure 1E). (D) H&E-stained sections from S.epi-monocolonized syngeneic grafts in hosts with anti-S.epi memory or a syngeneic, uncolonized graft in a naive host. A blinded pathologist identified (black arrows) and quantified (purple bars) abnormal mixed lymphocytic/neutrophilic infiltrates around hair follicles. Quantifications are plotted with the macroscopic 4-point score of the graft at sacrifice (orange bars). Original magnification ×20. (E) PCR band intensities of S.epi DNA isolated from skin swabs of S.epi-painted SPF hosts naive to (green) or with memory against (orange) S.epi. Intensities are normalized to a S.epi-positive control. An unpaired, 2-tailed t test was performed at each time point. (F) Graft scores of syngeneic hosts with or without anti–S. aureus memory that received skin grafts from SPF donors with or without S. aureus colonization. (C, E, and F) The area under the graft score curves was calculated for each mouse, and ANOVA with multiple comparisons was performed. Plots show 1 (F), 2 (E), 3 (B and C, green and blue lines), or 4 (C, orange line) independent experiments. **P < 0.005, ***P < 0.0005; mem., memory; col., colonized; d, day; ND, no data.