Loss of Il18r1 on CD8 T cells improves LCMV-induced hyperinflammation. (A) Weight loss throughout tamoxifen treatment and LCMV Armstrong infection (2e5 plaque-forming units per mouse). Il18tg and Il18tg;Il18r1^Δ8 mice were compared by mixed effects modeling because only 63% of Il18tg mice survived until experimental end point. (# indicates that mice succumbed 7-8 days after infection). No other mice succumbed to infection. (B) Anemia in surviving mice 10 days after infection. (C) Percentage of splenic CD8 T cells producing IFN-γ by intracellular flow cytometry after a 6 hour GP33 stimulation 10 days after infection. (D) Percentage of splenic CD8 and CD4 T cells expressing IL-18R1. (E) Percentage of splenic CD8 and CD4 T cells expressing PD-1 in mice directly ex vivo 10 days after infection. (A-E) Combined data from >3 experiments. P values in panels B and E are calculated using one-way analysis of variance (ANOVA) with Tukey post hoc test of comparisons between Il18tg, Il18r1^Δ8 and all other groups. Significance for comparisons between Il18tg and Il18tg;Il18r1^Δ8 groups are shown for adjusted P value < .05. PD-1, programmed cell death protein-1.