CLDN4 and Salmonella Infections: In this study, Salmonella infection activated TLR4-mediated immune responses, induced pro-inflammatory cytokines and chemokines expression (IFN-γ, TNF-α, IL-1β, and IL-8), and suppressed intestinal tight junction Claudin-1, Claudin-4 protein, and ZO-1 protein amounts in laying hens, which was in consistent with previous results using chicken models (3, 42).