ST2 blockade suppresses the immune response rather than LCMV infection. WT and Prf1^−/− mice were infected with LCMV, treated with either α-ST2 or control antibodies, and analyzed on day 8 p.i.; n = 4 mice per group. Analyzed by 2-way ANOVA; genotype (WT vs Prf1^−/−), ^###P < .001; treatment (control vs α-ST2), ^§§§P < .001; interaction between genotype and treatment, ***P < .001. (A) Splenic LCMV titer. Dotted line indicates limit of detection of plaque assay. Representative of 2 independent experiments. pfu, plaque-forming units. (B) Serum IFNγ level. Representative of 3 independent experiments.