TNF and infection: Of the two S. parasuis strains, NN1 possessed a higher capacity to induce IL-6, TNF-α, and MCP-1 production by primary astrocytes throughout the experiment, and by BV2 cells at 8 h post-infection, whereas BS26 induced higher IL-6 production by BV2 cells from 18 h post-infection (Figure 3A–F).