IL6 and infection: After 4 h of infection, the relative expression of tumor necrosis factor alpha (TNF-α) (Figure 4 A), interleukin-1β (IL-1β) (Figure 4 B), and IL-6 (Figure 4 C) in the APEC ΔclbH infection group were significantly decreased, compared with those in the APEC XM group (p < 0.01), while the expressions of above cytokines in APEC ΔclbH/pclbH group were similar with those in APEC XM group.