TNF and infection: At 8 h and 12 h post-infection, the levels of TNF-α, IL-6, and MCP-1 in both primary astrocytes and BV2 cells infected with the two S. parasuis strains were significantly higher than those of cells infected with S. suis strain P1/7, except for the MCP-1 in primary astrocytes at 12 h post-infection (Figure 3A–F).