An endotoxin and biologically active component of the Gram-negative bacterial cell wall that is a Toll-like receptor 4 (TLR4) agonist with potential immunostimulatory activity. Upon internalization, lipopolysaccharide (LPS) activates TLR4 which in turn activates the NFkappaB pathway, in addition to mitogen-activated protein kinases signaling pathways. This leads to the release of proinflammatory cytokines and stimulates an innate immune response against vaccine antigens.
