FIG. 3.

Spleens from naïve BALB/c mice (A and B) and BALB/c mice infected via subcutaneous injection with 20 CFU of Y. pestis CO92 (C and D) or Y. pestis CAC1 (E and F) were removed during necropsy on day 7 following the infectious challenge. Tissues were fixed, embedded in paraffin, thin sectioned, stained with hematoxylin-eosin, and viewed by light microscopy at a magnification of ×40. Captured images (A, C, and E) were enlarged fivefold to reveal loss of tissue architecture, necrotic polymorphonuclear leukocytes, massive cellular debris, and edema in plague-infected spleens (D and F) compared to uninfected tissue (B).