Cerebral histopathological changes following acute ileitis induction. C57BL/6 wildtype (WT; black circles) and TLR-9 deficient (TLR-9-/-; white circles) mice were perorally infected with 100 cysts of T. gondii ME49 strain on day 0 to induce acute ileitis. Naïve mice served as negative controls (N). (A) Cerebral histopathological changes (meninges and cortex) were assessed in H&E-stained paraffin sections of brains seven days following ileitis induction (ILE) applying a standardized histopathological score (as described in methods) and illustrated by representative photomicrographs (WT: upper panel, TLR-9-/-: lower panel; N: left panel, ILE: right panel). Arrows indicate inflammatory foci (100 × magnification, scale bar 100 μm). (B) Brain paraffin sections were stained for F4/80 by in situ immunohistochemistry and the average numbers of intracerebral macrophages and microglial cells were determined in six high power fields (HPF, 400 × magnification) per animal by light microscopy. (C) T. gondii DNA loads were determined in brain homogenates by semi-quantitative RT-PCR and normalized relative to the M. musculus ASL gene (Arbitrary Units). Numbers of analyzed mice (in parentheses), means (black bars) and levels of significance (P-values) as compared to the respective groups (determined by Mann-Whitney-U test) are indicated. Data shown were pooled from three independent experiments.