Figure 4.

Plasminogen activator inhibitor‐1 (PAI‐1) enhances lung pathology during Yersinia pestis infection. (A) Sections of formalin‐fixed lungs stained with hematoxylin and eosin from C57BL/6 or C57BL/6 PAI‐1 ^−/− mice inoculated with phosphate‐buffered saline (mock), 10⁴ colony‐forming units (CFUs) of Y. pestis, or 10⁴ CFUs of Y. pestis ∆pla. Representative images of inflammatory lesions are shown (n = 3). For each infection, the scale bar of the left image (× 2.5 magnification) represents 100 μm, and the scale bar of the right image (× 63 magnification) represents 50 μm. (B) Inflamed lesions were analyzed with imagej to calculate the area of inflammation. Data represent the lesion area (mm²) per field in two sections from three mice, each at × 2.5 magnification. (C) Quantification by ELISA of albumin levels in the bronchoalveolar lavage fluid (BALF) of C57BL/6 or C57BL/6 PAI‐1 ^−/− mice infected with 10⁴ CFU of Y. pestis or Y. pestis ∆pla, or mock‐infected. Data from two independent experiments are combined (n = 10 for each group), and error bars represent standard errors of the mean (SEMs). One‐way anova with Bonferroni's multiple comparison test was used to determine significance (*P ≤ 0.05; **P ≤ 0.01; ***P ≤ 0.001). NS, not significant.