TLR4 and infection: Infection with S. Typhimurium and S. Dublin led to a significant downregulation of TLR2, TLR3, TLR4, TLR5, and TLR7 in chicken macrophages HD11, whereas only a slight downregulation of TLR3 and TLR7 genes was observed in the S. Gallinarum infection group (Figure 6B).