Gross and microscopic analysis of lungs in Gprc5a-/- mice. (A) Surface of freshly removed, formalin-filled control lungs of 12 months old Gprc5a-/- mice lacks visible lesions. Scans of H&E stained lung sections (2X) and microscopic image (10X) shows no lesion. (B) A few surface lesions (double arrows) were seen after NNK treatment. Scans of H&E stained cross sections of NNK-treated lung (2X) and high magnification (10X) microscopic images demonstrate the appearance of several papillary adenomas. (C) NTHi treatment led to perivascular and peribronchiolar lymphocyte infiltration (**) and characteristic alveolar accumulation of acidophilic macrophages, often resulting in confluent areas of acidophil macrophage pneumonia (AMP, #). AMP strongly co-localized with the widespread appearance of NTHi-induced premalignant, hyperplastic lesions (10X). (D) NNK+NTHi combined treatment led to confluent lesions on the lung surface (double arrows). A high number of pulmonary adenomas and areas of AMP are seen on the H&E scans (2X). Pulmonary hyperplasia with co-localized acidophilic macrophages (#) and papillary adenocarcinomas (***) with surrounding of heavy inflammatory infiltration characterized by the accumulation of macrophages and lymphocytes are seen on the microscopic images (10X, scale bar = 100 μm).