Toll-like receptor activation of human cells by synthetic triacylated lipid A-like molecules

Abstract

Recognition of microbial molecules by mammalian host receptors is essential to mount an immune response. Hexaacylated LPS is the prototypic example of a bacterial molecule recognized by the receptor complex TLR4/MD-2 with its lipid A moiety, whereas bacterial lipopeptides are recognized by TLR2. Here we show that a series of synthetic triacylated lipid A-like molecules are weak Toll-like receptor (TLR) agonists (mainly TLR2 agonists) but very potent TLR4/MD-2 antagonists (submicromolar range). Not only do they block human cell responses to LPS but also to whole Gram-negative bacteria, and they inhibit the phagocytosis of Gram-negative bacteria. These compounds may represent promising immunomodulatory agents. © 2012 by The American Society for Biochemistry and Molecular Biology, Inc.