Figure 2.

Mouse lung histopathology after intranasal ricin challenge. Ten female BALB/c mice were challenged intranasally with 10 μg/kg ricin, and on day 2, post-challenge mice were anesthetized and their lungs processed for histopathology. The panels above are representative photographs of the pathological changes in mice exposed to ricin. (A) Inflammatory cell infiltrates (large arrowheads) surround bronchi (**) and blood vessels (*), and many alveoli are filled with proteinaceous fluid (edema) evident as pink staining material (small arrowheads). Note also the presence of perivascular edema and hemorrhage affecting the vessel adjacent to the small bronchus; (B) Alveoli are largely filled by fibrin (arrowhead), and there are also some degenerate neutrophils and necrotic debris evident; (C) Only a limited region of the epithelium lining a bronchus remains viable (arrowheads); the remainder is necrotic. Note the edema of the peribronchial connective tissue and infiltration by neutrophils, many of which are degenerate. The pathological changes evident can be compared to the normal mouse lung histology shown in (D).