FIG 4.

Peripheral responses to Y. pestis are MyD88 independent. Groups of WT or Myd88^−/− mice were challenged by intranasal infection with 2,000 CFU of Y. pestis CO92. On day 3 postinfection, the mice were euthanized, and blood and tissues were removed for further processing. (A) Percentage of mice with bacterial colonization of lungs or liver. (B to E) Sera were analyzed for cytokines IL-6 (B), TNF-α (C), IL-10 (D), and IFN-γ (E). (F to H) Representative liver histopathology (F and G) and quantification of lesion severity (H) for WT (F) and Myd88^−/− (G) mice at 72 hpi. Scale bar, 50 μm. Boxes in top panels indicate the zoomed-in sections shown in the bottom panels. Bars represent standard deviations. ND, not detected. Combined data from panel A (n = 17 WT mice, n = 12 Myd88^−/− mice; collected in 2 independent trials) were analyzed by the chi-square test. Combined data from panels B, C, and E (n = 40 WT mice, n = 36 Myd88^−/− mice; collected in 4 independent trials) and panel D (n = 30 WT mice, n = 26 Myd88^−/− mice; collected in 2 independent trials) were analyzed by the Mann-Whitney test; combined data from panel H (n = 10 per group; collected in 2 independent trials) were analyzed by an unpaired Student’s t test. *, P < 0.05; NS, not significant.