Much information has been learned about bacterial infection through the stimulation of macrophage cells with lipopolysaccharide (LPS), a bacterial antigen that acts as a Toll-like-receptor 4 (TLR-4) ligand to activate downstream immune responses65 and thus acts as a pathogen-associated molecular pattern to stimulate immune cells such as macrophages towards an inflammatory phenotype. This evidence concerns the gene TLR4 and bacterial infectious disease.