Figure 3. Starting number of NP₁₁₈-specific memory CD8 T-cells at the time of LCMV infection dictate secondary expansion and mortality in vaccinated PKO mice.

Five groups of naïve PKO mice (10 /group) received splenocytes from previously immunized donor PKO memory mice containing 8×10⁵ or 8×10⁴ or 8×10³ or 8×10² or 0 NP₁₁₈-specific memory CD8 T-cells one day before LCMV-Arm challenge .A) Phenotype of NP₁₁₈-specific memory CD8 T-cells prior to adoptive transfer as detected by direct ex-vivo L^d/NP₁₁₈ tetramer staining without antigen stimulation (top row) or intracellular IFN-γ after in vitro antigen stimulation (bottom row). Survival B) and morbidity measured as weight loss C) of the recipient PKO mice after LCMV-Arm infection (7 /group). D) Number of IFN-γ+ CD8+ T cells (mean + SD, n=3) in the spleen of recipient PKO mice in the absence (left panel) or presence (right panel) of NP₁₁₈ peptide stimulation at day 5 post LCMV infection. Data are representative of at least 2 independent experiments.