IL6 and infection: As shown in Figures 5(b) and 5(f), the infection resulted in a strong increase of IL-6 mRNA expression in both the hippocampal formation and cortex of WT mice (37.5 ± 9- and 97.5 ± 29-fold induction for infected WT in the hippocampus and cortex) while the infected TNFR1−/− mice showed a significant lower expression level (p < 0.05 and p < 0.001; Figures 5(b) and 5(f)).