Fig. 2.  Results of histopathologic examination of lung tissue in Toll-like receptor 4 (TLR4) wild-type (WT) and TLR4-mutant mice after ventilator-induced lung injury. Representative photomicrographs of hematoxylin-and-eosin staining (× 20 objective) of lungs from TLR4-WT (A–C ) and TLR4-mutant (D–F ) mice subjected to unventilated and tracheotomized control (CON), low tidal volume ventilation (LTV), and high tidal volume ventilation (HTV). HTV illustrates a marked increase in inflammatory cell infiltration, alveolar 2 septal thickening, and pulmonary edema in the lung in TLR4-WT mice (C ) compared with TLR4-mutant mice (F ).