Immunohistochemical localization of Claudin-4 in the lung. In lung tissue sections collected at 24 hours from sham WT mice (a) and from sham TNF-αR1KO mice (b), Claudin-4 were uniformly and continuously distributed along the alveolar epithelium and the vascular endothelium. On the contrary, a significant disruption of immunohistochemical localization signal for Claudin-4 was observed in the lung tissues 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 was found less irregular distribution pattern of Claudin-4 at 4 h (e) and at 24 hours (f) after carrageenan. Similarly, the treatment of WT mice with Etanercept (5 mg/kg administered s.c. 2 h prior carrageenan) were able to prevent carrageenan-induced distribution alteration of Claudin-4 at 4 h (g) and at 24 hours (h) after carrageenan. Figure is representative of at least 3 experiments performed on different experimental days.