Role of Toll-like receptors in health and diseases of gastrointestinal tract

Table 1 Toll-like receptors and known microbial ligands[4,7,18]

TLR family	Microbial ligands
Lipid ligands
TLR1	Tri-acyl lipopeptides (bacteria, mycobacteria)
TLR2	Lipoprotein/lipopeptides (a variety of pathogens)
	Peptidoglycan (Gram-positive bacteria)
	Lipoteichoic acid (Gram-positive bacteria)
	Lipoarabinomannan (mycobacteria)
	A phenol-soluble modulin (Staphylococcus epidermidis)
	Glycoinositolphospholipids (Trypanosoma Cruzi)
	Glycolipids (Treponema maltophilum)
	Porins (Neisseria)
	Zymosan (fungi)
	Atypical LPS (Leptospira interrogans and Porphyromonas gingivalis)
	Hemagglutinin (measles)
TLR4	LPS (Gram-negative bacteria)
	Fusion protein (respiratory syncytial virus)
	Envelope proteins (mouse mammary tumor virus)
	HSP60 (Chlamydia pneumoniae)
TLR6	Di-acyl lipopeptides (mycoplasma)
Nucleic acid ligand
TLR3	Double-stranded RNA (virus)
TLR7 or 8	U-rich ssRNA
TLR9	CpG DNA (bacteria)
Protein ligand
TLR5	Flagellin (bacteria)
Uropathogenic bacteria
TLR11	Uropathogenic bacteria
Ligand unknown
TLR10	?