Table 1.

Toll-like receptors and their corresponding ligands

Type of TLR	Microbial Pathogen Associated Molecular Patterns (PAMPs)(1)	Potential endogenous TLR ligands (DAMPs) in RA	Defined source in RA (synovial tissue, cells or fluid)
TLR2 (dimerization with TLR1or 6)	Lipoglycans (Mycobacterium) Lipoteichoic Acids (Gram-positive bacteria) Peptidoglycan (Gram-positive bacteria) Zymosan (Yeast)	HSP 60	Macrophage(2), synovial tissue*
		HSP70	fibroblast(2), macrophage(2) synovial tissue
		gp96	fibroblast(2), macrophage(2), synovial tissue and synovial fluid(2)
		HMGB-1	synovial tissue macrophages, synovial fluid
		Biglycan	fibroblast(2)
		Serum amyloid A	serum, synovial tissue
TLR4	LPS (Gram-negative bacteria) Mannan (Candida) Envelope protein (Virus)	HSP22	synovial tissue, fibroblast
		HSP 60	Macrophage(2), synovial tissue
		HSP70	fibroblast(2), macrophage(2) synovial tissue
		EDA fibronectin	synovial fibroblast, synovial fluid
		fibrinogen	Synovial tissue, synovial fluid
		low molecular weight hyaluronic acid	synovial fluid
		HMGB-1	synovial tissue macrophages, synovial fluid
		Biglycan	fibroblast
TLR5	Flagellin (Gram-negative bacteria)
TLR3	ds RNA (virus)	Undetermined	necrotic synovial fluid cells
TLR7	ss RNA(virus)
TLR8	ss RNA(virus)	Undetermined	necrotic synovial fluid cells
TLR9	CpG motif (bacteria, virus)	immunostimulatory CpG motifs	serum

^*Present is synovial tissue, the precise cell-type not identified