IL6 and infection: At 4 dpi, the expression of cytokines and chemokines G-CSF, IFN-γ, IL-6, KC, MCP-1, MIP-1α, MIP-1β, and RANTES in the brain of suckling mice was significantly upregulated after P9 infection (Figure 5B, p < 0.05, or 0.01, 0.001).