FIG. 5.

Histopathology of tracheobronchial lymph nodes. The left slide shows a quiescent node from the control animal; the middle panel shows the node from the infected animal at day 4 postinoculation, showing high cell density, dominance of small dense lymphocytes, macrophages with abundant cytoplasm (blue arrows), and golden to brown-black pigment granules and prominent high endothelial venules (green arrows); the right panel shows the node from the infected animal at day 7 postinoculation, showing diffuse edema, many activated macrophages (blue arrows) characterized by basophilic cytoplasm and nuclei with finely dispersed chromatin and a large central, magenta nucleolus (not visible at this magnification), dendritic cells (purple arrows), and hypertrophy of endothelial cells with large vesiculated nuclei (not visible at this magnification) in blood vessels (green arrows). Hematoxylin and eosin stain. Magnification, ×70.