The lipid A receptor consists of several subunits. Lipopolysaccharide binding protein (LBP) is a serum protein facilitating association of lipid A with CD14. The Lipid A-LBP-CD14 complex is further delivered to Toll-like receptor 4 (TLR4), which is essential for lipid A-mediated cellular activation. TLR4 associates with MD-2, which is required for surface expression and recognition of lipid A. In addition, the RP 10S-MD-1 complex mediates TLR4-mediated response in B cells and negatively regulates TLR4-mediated response in dendritic cells. Thus, lipid A receptor’s function varies among cell populations.
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