Immunohistochemical localization of ZO-1 in the lung. In lung tissue sections collected at 24 hours from sham WT mice (a) and from sham TNF-αR1KO mice (b), ZO-1 was uniformly and continuously distributed along the alveolar epithelium and the vascular endothelium. In contrast, a significant disruption of immuno-signal for ZO-1 was observed along the alveolar epithelium and the vascular endothelium in the lung sections of carrageenan-treated WT mice at 4 h (c) and at 24 hours (d) after carrageenan. In lungs of carrageenan-treated TNF-αR1KO mice, a more regular distribution pattern of ZO-1 along the alveolar epithelium and the vascular endothelium was found at 4 h (e) and at 24 hours (f), thus indicating that in carrageenan-treated TNF-αR1KO mice carrageenan treatment provokes a lower degree of disorganization of ZO-1. Similarly, the treatment of WT mice with Etanercept (5 mg/kg administered s.c. 2 h prior carrageenan) visibly and significantly reduced the disorganization of ZO-1 in the lung tissues collected at 4 h (g) and at 24 hours (h). Figure is representative of at least 3 experiments performed on different experimental days.