TLR2, TLR4, and TLR5 play important roles in bacterial infection: TLR4 recognizes LPS, a major cell wall component of Gram-negative bacteria, whereas TLR2 and TLR5 recognize peptidoglycan (PGN), another bacterial wall component, and flagellin (FLG), respectively. This evidence concerns the gene TLR4 and bacterial infectious disease.