IL6 and infection: In the brain, the protein levels of the pro-inflammatory cytokines IL-1β, IL-12 (Figure 2C) and IL-6 (data not shown), were comparable to control levels when measured at day 7 post-infection, but levels of these cytokines increased gradually to become significantly increased at 21 days post-infection (Figure 2C, IL-1β 4.7-fold P < 0.05, IL-12 4.4-fold P < 0.05).