Comparison of lung phenotype of wildtype (WT) and SP-C/TNF-α (TNF) mice. (A-D) Mice were euthanized and lungs were inflated to 25 cm H2O static pressure by intratracheal instillation of 4% paraformaldehyde in PBS. Sections from WT (A, C) and TNF (B, D) mice were stained with hematoxylin and eosin. (A) WT lungs (original magnification 40×). (B) TNF lungs exhibited chronic inflammation and air-space enlargement (original magnification 40×). Comparison of WT lungs at higher magnification (C) to TNF lungs (D) revealed thickened interstitial areas (original magnification 200×). (E) Effects of PM inhalation on lavage cytology. Cells were recovered by bronchoalveolar lavage of mice exposed to EHC-6802 (0, 42 mg/m3) and euthanized 0 or 24 h post-exposure. Numbers of all cell types were significantly increased in TNF mice relative to their WT littermates (Genotype main effect, p < 0.001). There were no significant effects of particle exposure within each genotype. MNGC, multi-nucleated giant cells.