Fig. 4

VM cells dominate the memory response of naïve aged mice to de novo virus infection. a CD8 TM (CD44^High/CD49d^High) and VM (CD44^High/CD49d^Low) cells were FACS-sorted from naïve aged C57BL/6 and naïve aged B6.CD45.1 mice, respectively, and adoptively transferred into T cell deficient TCR βδ−/− mice at a 1:1 ratio, with CD8 depleted splenocytes from naïve young B6CD90.1 mice (2–3 months). The mice were infected with influenza virus and the responding CD8 T cells originating from TM or VM donors analyzed at 12 days post infection. b Flow cytometry gating strategy used to identify the donor populations in the lung: distinguished by CD90.2⁺CD45.1⁻ cells for donor aged C57BL/6, CD90.2⁺CD45.1⁺ for donor aged B6.CD45.1, and CD90.2⁻CD45.2⁻ for donor young B6.CD90.1. c Representative FACS plots from two individual recipient mice, gated on donor CD8 T cells from the lung. Data show that the response of cells specific for a representative influenza-specific tetramer, PA₂₂₄, was mediated almost exclusively by VM cells. d Representative FACS plots from two mice, gated on VM donor PA₂₂₄-specific cells, showed upregulated expression of CD49d. e The epitope-specificity of the TM donor, VM donor, and intact WT control memory response are represented by colors. The data represent two independent experiments