FIG. 3.

Pathology of hepatic and central nervous system lesions of STAT1−/− mice following i.p. injection with WSN virus. (A) Hematoxylin-eosin-stained section of liver showing multiple aggregates of inflammatory cells within the hepatic parenchyma. Magnification, ×98. (B [magnification, ×197] and C [magnification, ×394]) Sections reacted with polyclonal antibody against influenza A virus. Infected cells are bright red. Only a fraction of inflammatory cells constituting the liver lesions show positive staining for influenza virus antigens. Multiple hepatocytes stain strongly, some showing only nuclear staining, indicating an early phase of virus replication. In other hepatocytes, viral proteins are also present in the cytoplasm. (D) Section of brain with a focus staining positively for the presence of viral antigen (magnification, ×98). In panel E (magnification, ×394), it can be appreciated that many of the red-staining cells are neurons. Glial cells within the focus also stain positively. (F) Single infected ependymal cell (magnification, ×394).