Figure 1.

Chlamydia muridarum associated bronchointerstitial pneumonia, lung, NOD.Cg-Prkdc^scidIl2rg^tm1Wjl/SzJ mice. (a) Multifocal to regional bronchointerstitial pneumonia. Hematoxylin and eosin stain (HE). (b) Histiocytic and neutrophilic bronchointerstitial pneumonia with intracytoplasmic chlamydial inclusions (CIs) in bronchiolar epithelium (arrows). HE. (c) Interstitial and alveolar spaces are expanded by histiocytic and neutrophilic inflammation admixed with fibrin, pyknotic and karyorrhectic debris, and intralesional CI. HE. (d) Histiocytic and neutrophilic bronchointerstitial pneumonia with necrotic debris, degenerate neutrophils, bronchiolar epithelial degeneration, and intracytoplasmic CI in bronchiolar epithelium (arrows). HE. (e) High magnification CI within bronchiolar epithelial cells. HE. (f) Chlamydia antigen in inclusions within bronchiolar epithelial cells and the bronchiolar lumen. Immunohistochemistry (IHC) for Chlamydia major outer membrane protein antigen (MOMP). (g) Chlamydia nucleic acid in inclusions in bronchiolar epithelial cells and extracellularly the bronchiolar lumen. In situ hybridization (ISH) for Chlamydia RNA. (h) Immunolabeling of macrophages within areas of inflammation in the interstitium and peribronchiolar regions. IHC for F4/80. (i) Immunolabeling of neutrophils in bronchioles and throughout the alveolar interstitium. IHC for Ly6G.