After infecting shTLR4 cells and subsequently analyzing the mRNA levels of the pro-inflammatory cytokines TNF-α, IL-1β, IL-8, and IL-6 (Figure 8A–D), we observed that infection with the co-culture of P. gingivalis and F. nucleatum triggered significant increases in the expressions of TNF-α (3.0-fold change) and IL-8 (7.4-fold change) in shTLR4 cells compared with those of the non-infected control. Here, CXCL8 is linked to infection.