PAI-1 deficiency impairs host defense against Klebsiella pneumonia. (A-C) Wt and PAI-1^−/− mice were inoculated intranasally with 10⁴ CFU K pneumoniae. d-dimer was measured in lung homogenates at 0, 24, and 48 hours after infection (A). Survival was monitored (B) and bacterial load was determined at 24 and 48 hours after infection (C). Data are means ± SE of 8 mice per genotype at each time point. Survival was evaluated using 12 mice per genotype. *P < .05 versus Wt mice at the same time point. **P < .01.