Genetic deletion of PA T2SS (ΔxcpQ), but not T3SS exotoxins (ΔexoTUY), attenuates alveolar–capillary barrier disruption in thrombocytopenic Mpl^−/−mice. Gross appearance of BAL fluid (A), BAL OD₅₄₀ measurements (B), BAL protein concentrations (mg/mL) (C), BAL IgM (ng/mL) (D), BAL neutrophil counts/mL (E), or lung MPO activity (U/left lung) (F) were obtained in Mpl^−/− mice 20 hours following IT administration of vehicle or cell-free SN from PA14 or PA14ΔxcpQ strain (n = 5 mice in vehicle group, n = 8 mice in PA14 and PA14ΔxcpQ groups). In separate experiments, gross appearance of BAL fluid (G), BAL OD₅₄₀ measurements (H), and BAL protein concentrations (mg/mL) (I) were obtained in Mpl^−/− mice 20 hours following IT administration of vehicle or cell-free SN from PA14 or PA14ΔexoTUY (n = 4 mice in vehicle group, n = 8 mice in PA14 and PA14ΔexoTUY groups). Each tube or point represents an individual mouse, and the group median is displayed. Statistical comparison by Kruskal-Wallis test with Dunn’s test for multiple comparisons (lines represent post hoc analysis). *P < .05, **P < .01, and ***P < .001.