Fig. 1.

Memory cells from naïve aged mice can respond to de novo infection with influenza. a Sorted CD44^High memory CD8 T cells from naïve aged (18–22 months) mice were co-transferred with CD8 T cell-depleted splenocytes from young mice into T cell deficient TCR βδ−/− mice, infected with influenza virus, and the responding CD8 T cells analyzed at 12 days post infection. b The epitope-specific CD8 T cell response of 19 individual aged mice is indicated by colors and a young WT control mouse is shown