TLR4 and influenza: Human monocytes have been tested following Toll-like receptor 4 (TLR4) stimulation [137], human dendritic cells were exposed to E. coli lipopolysaccharide, influenza, or interferon-β (IFN-β) [138], human monocytes were treated with interferon-γ (IFN-γ) or lipopolysaccharide [139], monocyte-derived macrophages were infected with Listeria monocytogenes or Salmonella typhimurium [140], while primary monocytes were exposed to ligands activating Toll-like receptor pathways (TLR1/2, TLR4, and TLR7/8) and to influenza virus, in samples from Africans and Europeans [141].