Differential homing preference of CD27^hi and CD27^lo memory cells within the lung after lethal respiratory VACV-WR infection. Mice that received CD8⁺CD44^hi CD27^hi or CD27^lo memory T cells in Fig. 1 were analyzed on day 7 after infection. IF analysis of frozen lung sections from VACV-infected CD8⁺CD44^hi CD27^hi (A and B) or CD8⁺CD44^hi CD27^lo (C and D) recipient mice stained for CD45.1 (red) and CD8 (magenta). DAPI (blue) and ActinGreen (green) were used to visualize nuclei and lung morphology, respectively. Bars, 50 µm. Lung parenchyma, airway lumen, bronchial arteries are delineated by broken lines. The marked areas are shown in higher magnification to the right of each panel. CD45.1⁺ (red) donor cells are delineated with white arrows. Endogenous CD8 T cells could also be identified (magenta; blue arrows). (E) IF analysis of lung sections from aforementioned CD27^lo recipient mice stained with CD45.1 (magenta), NG2 (green), DAPI (blue), and CD34 (red) or (F) αSMA (red). Bars: (E and F) 10 µm. Results are representative of three experiments each with three mice per group.