LCMV-infected C57BL/6 mice were treated daily with IL-7 or PBS between days 7 and 14 after infection. (A and B). On day 43 after infection, the number of epitope-specific CD8 T cells in the spleen was enumerated by staining with MHC I tetramers. Each data point represents an individual mouse. (C) Cell surface phenotype of memory CD8 T cells. On day 43 after infection, splenocytes were stained with anti-CD8, MHC I tetramers, anti-CD127, and anti-CD62L. The fluorescence activated cell sorting plots are gated on tetramer-binding CD8 T cells, and the numbers are the percentages of cells among epitope-specific cells in the respective quadrants ± SD. (D) Cytokine production by memory CD8 T cells. The ability of LCMV-specific memory CD8 T cells to produce IFN-γ, TNF, and IL-2 was assessed by intracellular cytokine staining; dot plots are gated on IFN-γ–producing CD8 T cells, and the numbers represent cells in each quadrant as a percentage ± SD among IFN-γ–producing epitope-specific CD8 T cells. The data in C and D were derived from analyses of 5 mice/group.