Histopathologic evaluation of lung tissue from wildtype (WT) and Cyp2abfgs-null mice following exposure to filtered air (FA) or environmental tobacco smoke (ETS) via inhalation. Paraffin-embedded, formalin-fixed lung tissue sections from WT and Cyp2abfgs-null mice (adult female, n = 3) were H&E stained and evaluated for the occurrence of pathological changes following 1 week of daily FA or ETS inhalation exposures as described in Materials and Methods section. Representative images of nodules of inflammations (NIFs) from ETS-exposed WT and Cyp2abfgs-null mice are shown at ×4 magnification. Scale bar is 200 µm. NIFs were observed in both peribronchiolar (arrow) and perivascular (*) regions of ETS-exposed WT mice. However, NIFs were observed only in perivascular, but not in peribronchiolar, regions of ETS-exposed Cyp2abfgs-null mice. Images of NIFs observed in FA-exposed WT and Cyp2abfgs-null mice are shown at ×10 magnification with a 100 µm scale bar.