Fig 3.

Expression of MHC II in hippocampus of infected TG relative to infected NT mice. Signal was evaluated in the hemisphere opposite the inoculation site. (A) Representative expression of MHC II in infected NT and TG mice (NT and TG, respectively) and the uninfected controls (NT and TG Uninf) at 5 days p.i. (n = 4/group). Shown are paraformaldehyde-fixed frozen sections, with immunoperoxidase staining and hematoxylin counterstain, at magnifications of ×4 (left four panels) and ×40 (right). Virus-induced cytopathic effects or cellular inflammatory infiltrates affecting the granular cell neurons of the dentate gyrus (GrDG) and pyramidal cell neurons of the CA1, CA2, and CA3 regions of the hippocampus are not present at this early p.i. interval, although induced MHC II expression on parivascular and parenchymal microglia is evident in TG mice. The signal levels between uninfected TG and NT mice and infected NT mice were equivalent. (B) Quantification of pixel counts from digitized images (number of positive pixels/total number of pixels) shows that the increased staining in infected TG relative to infected NT mice is statistically significant (P < 0.05, t test).