Toll-like receptors on the fork roads between innate and adaptive immunity.

There is a permanent interaction amid the innate and adaptive immune systems that leads to a defensive immune response against pathogens and contributes substantially to self-nonself discrimination. Toll-like receptors (TLRs) are essential molecules of the innate immune system that stimulate numerous inflammatory pathways and harmonize systemic defense against a wide array of pathogens. In addition to identifying unique molecular patterns associated with various sections of pathogens, TLRs may also recognize a number of self proteins and endogenous nucleic acids. Several reports have indicated that inappropriate stimulation of the TLR pathway via endogenous or exogenous ligands in animal models or humans may lead to the induction and/or prolongation of autoimmune response and tissue injury.