Innate recognition of lipopolysaccharide by Toll-like receptor 4–MD-2

Toll-like receptors (TLRs) are pathogen recognition molecules that activate the immune system as part of the innate immune response. Microbial recognition by TLRs plays a crucial role in the host immune system's decision to respond or not to a particular microbial infection. Lipopolysaccharide (LPS), a membrane glycolipid of Gram-negative bacteria, exhibits strong immunostimulating activity among TLR ligands and has been studied in great detail. Recent studies have shown that cell surface TLR4–MD-2 physically interacts with LPS and triggers the release of an LPS signal, revealing a host–pathogen interaction mediated by TLR.