The role of Toll-like receptors (TLRs) in stroke

Toll-like receptors (TLRs) recognizing the exogenous pathogen-associated molecular patterns (PAMPs) are part of the innate immune system that plays a role in various challenging interactions between the neurons and the immune system. Stroke as a major injury to the central nervous system (CNS) is one of the hot points of such cross-talk. The various roles of the different types of TLRs in stroke can be classified into three major categories: (1) the hazardous effect of TLRs with a focus on the part in poststroke neurodegeneration, (2) the beneficial effect of those types of TLRs that exert a neuroprotective effect following an ischemic insult, and (3) the role of TLRs in immunomodulation on one hand and the possible autoimmunity as a consequence of neuronal injury due to an ischemic attack on the other hand. However, the mentioned functions of TLRs, similar to many other parts of the immune system, might overlap in many aspects. The current review article, including both experimental and clinical studies, is an attempt to bring together the studies that have investigated the roles of TLRs in stroke while referring to the apparent controversies in this field, with pointing out the new ideas for further considerations.