Lipopolysaccharide (LPS) is the major constituents of the outer membrane of Gram-negative bacteria. LPS recognition and signal transmission are key events in the host defense reaction towards Gram-negative bacteria and are associated with many disorders. Multiple signaling pathways are involved in the response to LPS. With the help of LPS-binding protein and CD14, TLR4 binds with LPS, then recruits myeloid differentiation factor 88 and IL-1 receptor-associated kinase, and further phosphorylates and activates TNF receptor associated factor 6 (TRAF6). The activated TRAF6 leads to the activation of transcription factor NF-kappaB and MAP kinase's pathways that involves in LPS-induced cellular responses and the production of proinflammatory cytokines such as TNF-alpha, IL-6 and IL8.