Relatively weak recall responses because of more LCMV-specific CD8 T cells in LCMV-immune HP mice. (A) LCMV-immune mice were rechallenged with LCMV. Cells were stimulated with LCMV-specific peptides, and the numbers of CD8⁺, CD4⁺ (left; means ± SD) or each LCMV-specific CD8⁺ T cells were counted (right; means ± SD). This is a representative result from 2 experiments with 2 to 7 mice per group. (B) Dot plots show LCMV-specific CD8 T cells from a representative rechallenged LCMV-immune HP or WT mouse. Numbers refer to percentage of cells in designated quadrants. (C) LCMV-immune mice were challenged with VV-GP, and their splenocytes were harvested at day 6. Cells were stimulated with LCMV-specific GP peptides, and then the cell numbers of total CD8⁺ (left; means ± SD) or of LCMV- and VV-specific CD8⁺ T cells were counted (right; means ± SD). This is a representative result from 2 repeated experiments with 2 mice per group. (D) 1.5 × 10⁷ cells, 5 × 10⁶ cells, or 3 × 10⁶ cells either from Ly5.1 LCMV-immune HP or Ly5.1 WT mice were adoptively transferred into Ly5.2 naive B6 mice. The day after transfer, mice were infected with LCMV, and their splenocytes were harvested after 6 days. Cells were stimulated with LCMV-specific peptides and each LCMV-specific CD8⁺ T cell was counted (means ± SD). This is a representative result from 2 repeated experiments with 3 mice per group.