Antiviral T cells noncytopathically clear virus from microglia. (A) Representative FACs plots show the frequency of granzyme B⁺ CD8⁺ P14 T cells (blue boxes) in the brains of day 12 immunotherapy recipients. Day 6 LCMV meningitis mice were used as a positive control for this experiment. FACs plots are gated on CD45⁺ CD8⁺ Thy1.1⁺ cells. The bar graph shows the mean ± SD frequency of granzyme B⁺ antiviral CTLs (n = 4 mice per group; two independent experiments; *, P < 0.05). (B) Representative FACs plots show the frequency of Annexin V⁺ and 7-AAD⁺ microglia at day 12 after immunotherapy. Plots are gated on CD45^lo/int Thy1.2⁻ Gr1⁻ CD11b⁺ cells. The bar graph shows the frequency (mean ± SD) of Annexin V⁺ microglia (n = 3 mice per group; three independent experiments). (C) Representative FACs plots show BrdU expression in microglia (CD45.2^lo Thy1.2⁻ Ly6C⁻ Ly6G⁻ CD11b⁺) from carrier mice and day 9 immunotherapy recipients. A plot from a control mouse that did not receive BrdU is also shown. The frequencies (mean ± SD) of BrdU⁺ microglia are provided in the bar graph (n = 4 mice per group; three independent experiments; *, P < 0.05). (D) The frequency of LCMV⁺ microglia was determined flow cytometrically at the denoted time points after immunotherapy and compared with untreated carrier mice. Data are plotted as mean ± SD (n = 3 mice per group; two independent experiments; *, P < 0.05). (E) The normalized fraction of LCMV⁺ microglia was calculated at day 30 after immunotherapy for mice that received B6 or IFNγ^−/− memory cells. Data are plotted as mean + SD (n = 7 mice per group from two independent experiments; *, P < 0.05).