Lipopolysaccharide(LPS)is the major component of the outer membrane of gram-negative bacteria.LPS also serves as major target of innate immune system.The recognition of LPS by macrophages,granulocytes and dendritic cells and the subsequent triggering and activation of intracellular signal transduction cascade are responsible for the activation of early innate host defense against the intrusion of Gram-negative pathogens.LPS is closely associated with fever,Gram-negative sepsis,septic shock and eventually death.