mHVEM^−LIGHT mice are more susceptible to Y. enterocolitica infection. Co-housed littermates were infected with 1.0 × 10⁸Y. enterocolitica. (A) Survival curves in day 7 and day 12 experiments. *, P < 0.05 for log-rank test. (B) Changes in body weight (percentage of baseline). The weights of mice that died during the experiment were carried forward. Data shown are mean ± SEM. *, P < 0.05; **, P < 0.01; ***, P < 0.001 (+/+ vs. KI/KI) or ^#, P < 0.05 (+/+ vs. KI/+) for two-way repeated measures ANOVA with Bonferroni’s multiple hypothesis correction. Because of the number of mice that could be handled, experimental data were done at different times with different bacterial cultures. (C) Representative H&E staining to detect necrotic areas and WS silver staining to detect bacteria in splenic and hepatic sections from the indicated mice at 7 d after infection. Scale bars, 100 µm. White dotted lines indicate necrotic areas, and black dotted lines indicate Y. enterocolitica. The histopathologic scores of H&E sections were evaluated as described in Materials and methods for all mice analyzed from day 7 experiment in A and B (left panels). Mice that survived to at least day 6 are indicated with circles, and mice that died earlier are indicated with triangles. Data shown are median. *, P < 0.05 for two-way ANOVA.