Figure 1.

Bystander memory CD8 T cell responses decrease with time after initial antigen encounter. (A) Experimental Design. Mice received adoptive transfer of naïve P14 cells and were infected with LCMV-Armstrong. Either 30 days (earlyM) or >8 months (lateM) after LCMV infection, mice were infected with Vir LM. Analysis was performed 20 h following Vir LM infection. (B) Representative histograms of bystander IFN-γ production by earlyM (left) or lateM (right) P14 cells (top), endogenous CD11a^hi/CD8α^lo Ag-experienced cells (middle), or endogenous CD11a^lo/CD8α^hi naïve cells (bottom). (C) Summary bar graphs of the percentage of earlyM and lateM P14 cells or endogenous Ag-experienced cells producing IFN-γ or GrB 20 h after Vir LM infection of the indicated dose. n = 5 mice/group. Representative data from 1 of 3 independent experiments. Error bars represent mean ± SEM. Unpaired t-test; NS, not significant, *p < 0.05, **p < 0.01.