Bacterial lipopolysaccharides are recognized in mammals by a receptor complex composed of CD14, Toll-like receptor (TLR)-4 and MD-2. Transduction of signaling is achieved following the recruitment of a combination of four Toll-interleukin-1 resistance (TIR)-domain-containing adapter molecules, which provide a structural platform enabling the recruitment and activation of downstream effectors essential for pathway-specific transcription factor activation and inflammatory gene expression.