Figure 5.
Platelets are in alveoli during recovery from pulmonary inflammation. Bacterial pneumonia was induced in WT mice. (A–F) Ultrathin cross-sectioned lung tissue imaged by transmission electron microscopy WT mice after inducing pneumonia showing neutrophils (N) in close proximity to platelets (P) within the lung intra-alveolar space. Bacterial pneumonia was induced in WT, DEREG, and Mrp8+/+iDTR+DT (receiving DT) mice by i.t. instillation of viable K. pneumoniae (1.5 × 107 CFUs/mouse; exemplary images from at least two independent experiments with three mice in each group, black scale bars in A and D equal 10 µm, scale bars in B, E, and F equal 2 µm, and scale bar in C equals 1 µm). (G) Platelet counts in the BAL in MRP8-iDTR and DEREG mice. (H and I) Concentrations of the cytokines TGFβ (H) and IL-10 (I) in the BAL fluid were analyzed by ELISA (data pooled from at least two independent experiments with four to six mice in each group; Mann-Whitney test was used for statistical analysis, *, P < 0.05). (J–L) Confocal image of lung tissue with terminal alveolae from WT mice (J) 3 d after induction of pneumonia with (K) 3D reconstruction and (L) exemplary display of a single confocal plane to identify neutrophils (Ly6G, green) and platelets (CD41, red) within pulmonary capillaries stained with PECAM-1 antibody (CD31, gray). Scale bar, 50 µm. Lower insert displays exemplary 3D reconstruction of direct interaction of platelets (CD41, red) and neutrophils (Ly6G, green). (M and N) Confocal image of lung tissue from WT mice (M) 5 d after induction of pneumonia with (N) exemplary display of a single confocal plane to identify neutrophils (Ly6G, green) and platelets (CD41, red) within pulmonary capillaries stained with PECAM-1 antibody (CD31, gray). Scale bar, 50 µm; inserts with higher magnification in upper left corner and lower insert displays exemplary 3D reconstruction of direct interaction of platelets (CD41, red) and neutrophils (Ly6G, green). White arrows indicate sites of direct platelet–neutrophil interactions. (O and P) Confocal image of lung tissue from Mrp8+/+iDTR+DT mice (O) 5 d after induction of pneumonia with (P) exemplary display of a single confocal plane to identify neutrophils (Ly6G, green) and platelets (CD41, red) within pulmonary capillaries stained with PECAM-1 antibody (CD31, gray). Scale bar, 50 µm; inserts with higher magnification in upper left corner. (Q) Confocal image of lung tissue from WT mice 5 d after induction of pneumonia with exemplary display of a single confocal plane to identify T reg cell (CD25, yellow) and platelet (CD41, red) aggregates within the lung tissue. Scale bar, 50 µm; lower insert displays exemplary 3D reconstruction of direct interaction of platelets (CD41, red) and T reg cells (CD25, yellow). Bacterial pneumonia was induced in WT and Mrp8+/+iDTR+DT (receiving DT) mice (inserts with higher magnification in upper left corner). (R and S) Platelet accumulation in the alveolar space (R) and the quantification of platelet–neutrophil interactions (S) was analyzed by confocal image of lung tissue from WT mice 3 and 5 d after induction of pneumonia (exemplary images from at least three independent experiments with three mice in each group; Mann-Whitney test was used for statistical analysis, *, P < 0.05). PLT, platelet.

Platelets are in alveoli during recovery from pulmonary inflammation. Bacterial pneumonia was induced in WT mice. (A–F) Ultrathin cross-sectioned lung tissue imaged by transmission electron microscopy WT mice after inducing pneumonia showing neutrophils (N) in close proximity to platelets (P) within the lung intra-alveolar space. Bacterial pneumonia was induced in WT, DEREG, and Mrp8+/+iDTR+DT (receiving DT) mice by i.t. instillation of viable K. pneumoniae (1.5 × 107 CFUs/mouse; exemplary images from at least two independent experiments with three mice in each group, black scale bars in A and D equal 10 µm, scale bars in B, E, and F equal 2 µm, and scale bar in C equals 1 µm). (G) Platelet counts in the BAL in MRP8-iDTR and DEREG mice. (H and I) Concentrations of the cytokines TGFβ (H) and IL-10 (I) in the BAL fluid were analyzed by ELISA (data pooled from at least two independent experiments with four to six mice in each group; Mann-Whitney test was used for statistical analysis, *, P < 0.05). (J–L) Confocal image of lung tissue with terminal alveolae from WT mice (J) 3 d after induction of pneumonia with (K) 3D reconstruction and (L) exemplary display of a single confocal plane to identify neutrophils (Ly6G, green) and platelets (CD41, red) within pulmonary capillaries stained with PECAM-1 antibody (CD31, gray). Scale bar, 50 µm. Lower insert displays exemplary 3D reconstruction of direct interaction of platelets (CD41, red) and neutrophils (Ly6G, green). (M and N) Confocal image of lung tissue from WT mice (M) 5 d after induction of pneumonia with (N) exemplary display of a single confocal plane to identify neutrophils (Ly6G, green) and platelets (CD41, red) within pulmonary capillaries stained with PECAM-1 antibody (CD31, gray). Scale bar, 50 µm; inserts with higher magnification in upper left corner and lower insert displays exemplary 3D reconstruction of direct interaction of platelets (CD41, red) and neutrophils (Ly6G, green). White arrows indicate sites of direct platelet–neutrophil interactions. (O and P) Confocal image of lung tissue from Mrp8+/+iDTR+DT mice (O) 5 d after induction of pneumonia with (P) exemplary display of a single confocal plane to identify neutrophils (Ly6G, green) and platelets (CD41, red) within pulmonary capillaries stained with PECAM-1 antibody (CD31, gray). Scale bar, 50 µm; inserts with higher magnification in upper left corner. (Q) Confocal image of lung tissue from WT mice 5 d after induction of pneumonia with exemplary display of a single confocal plane to identify T reg cell (CD25, yellow) and platelet (CD41, red) aggregates within the lung tissue. Scale bar, 50 µm; lower insert displays exemplary 3D reconstruction of direct interaction of platelets (CD41, red) and T reg cells (CD25, yellow). Bacterial pneumonia was induced in WT and Mrp8+/+iDTR+DT (receiving DT) mice (inserts with higher magnification in upper left corner). (R and S) Platelet accumulation in the alveolar space (R) and the quantification of platelet–neutrophil interactions (S) was analyzed by confocal image of lung tissue from WT mice 3 and 5 d after induction of pneumonia (exemplary images from at least three independent experiments with three mice in each group; Mann-Whitney test was used for statistical analysis, *, P < 0.05). PLT, platelet.

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