Lung entry affects CXCR3 expression on central-like memory cells in a time- and virulence-dependent fashion and is cytokine driven. Memory CD27^hiCXCR3^hi CD8 T cells were sorted from spleens of CD45.1+ SJL mice, i.v. transferred into naive (CD45.2⁺) WT (A–G), IL-12p40^−/− (H–K and N), and IL-15^−/− (H–O) recipient mice that were i.n. infected next day with VACV-WR (10⁶, 10⁴, and 10³ PFU) or attenuated VACV-NYCBOH (NY; 10⁵ PFU) as indicated. Lung mononuclear cells were harvested on day 5 (A), 6 (A), and 7 (A–C and H–K) after infection and stained for CXCR3 and KLRG1 expression as in Fig. 4 F. (A, top) Representative plots of gated CD8⁺CD44⁺ T cells staining for CD45.1 on the indicated days after infection; (bottom) Representative plots showing CXCR3 and KLRG1 expression gated on CD8⁺CD44⁺CD45.1⁺ donor cells. (B) Representative plots showing CXCR3 and KLRG1 expression gated on CD8⁺CD44⁺CD45.1⁺ donor cells recovered from the LNs, blood, and spleen. (C and H) Representative plots of gated CD8⁺CD44⁺ T cells staining for CD45.1 (top) and CXCR3/KLRG1 expression gated on total CD45.1⁺ (middle) and CD45.1⁺ B8R_20-27/K^b-tetramer⁺ (bottom) cells on day 7. Total numbers of CD45.1⁺ (D), CD45.1⁺ B8R_20-27/K^b-tetramer⁺ (E), CD45.1⁺KLRG1⁺ (gate 2; F), and CD45.1⁺KLRG1⁺CXCR3^lo (gate 3; G) presented as the mean ± SEM of two separate experiments containing three mice per group. (I) Representative plots of gated CD8⁺CD44⁺CD45.1⁺ B8R_20-27/K^b-tetramer⁺ LN cells staining for CXCR3/KLRG1 expression on day 7. Representative plots for CD107a/IFN-γ (J) and Eomesodermin (K) staining gated on CD8⁺CD44^hiCD45.1⁺ cells recovered from the lung. (L) Total lung mRNA transcript levels of 84 cytokine and chemokine genes were measured from the same groups as in H and presented as scatter plot. Fold change in gene expression between CD27^hiCXCR3^hi WT and IL-15^−/− recipients is presented. (M and N) CD27^hiCXCR3^hi (M) and total CD8⁺CD44⁺ CD8 T cells (containing a mixture of CD27^hiCXCR3^hi and CD27^loCXCR3^lo cells; N) were sorted from spleens of CD45.1⁺ SJL mice, i.v. transferred into naive (CD45.2⁺) WT, IL-12p40^−/−, and IL-15^−/−-recipient mice that were i.n. infected the next day with a lethal inoculum of VACV-WR. Mean percent survival curves are shown. (O) Representative plots of gated CD8⁺CD44⁺ T cells staining for CD45.1 (left) and CXCR3/KLRG1 expression (right) gated on CD45.1⁺ B8R_20-27/K^b-tetramer⁺ lung cells on day 7. Results are mean (n = 6–8 per group) from two experiments with similar results. *, P < 0.05; **, P < 0.01 (two-tailed Student’s t test or Mantel-Cox test used in M and N).