Several TLRs not only have the ability to recognize more than one ligand, but often recognize ligands with completely different chemical structures. Such TLR activation does not occur under normal circumstances but only when there is a change in the environment that either leads to the release of endogenous ligands from a cellular compartment, or leads to the modification of endogenous mediator that gives them the ability to activate TLRs (110, 111) . Because of the association of many endogenous ligands with tissue injury, the nomenclature of DAMPs has been suggested. The best characterized DAMPs include those products released from cells in response to stress or undergoing abnormal death, including Hsp60, Hsp70, the extra domain A of fibronectin, oligosaccharides of hyaluronic acid and high-mobility group box 1 (HMGB1). Most of these ligands act as agonists of TLR2 or TLR4, or both receptors (112) .