Increased mortality in bleomycin-injured PN-1^−/−mice.PN-1^−/− mice and their PN-1^+/+ littermates were subjected to bleomycin-induced lung injury (2 mg/kg) by intratracheal instillation. Percentages of surviving mice were plotted over a 14-day period after bleomycin treatment. Log-rank test was used to compare the difference between PN-1^−/− and PN-1^+/+ mice (n = 25 per group; P ≤ .0001). The proportion of survival was determined based on euthanasia criteria. Animals that lost 20% of their body weight were euthanized.