Role of Circulating Immune Cells in Stroke and Preconditioning-Induced Protection

Stroke activates an inflammatory response that results in the infiltration of peripheral immune cells into the ischemic area, contributing to exacerbation of tissue damage. However, evidence indicates that inflammatory cell infiltration can also promote neuroprotection through regulatory immune cells that mitigate injury. These immune regulatory cells may also be important mediators of neuroprotection associated with preconditioning, a phenomenon whereby small exposure to a potential harmful stimulus is able to induce protection against a subsequent ischemic event. The elucidation of mechanisms that allow these immune cells to confer neuroprotection is critical to developing new therapeutic strategies against acute stroke. In the present review, we discuss the dual role of peripheral immune cells in stroke-related brain injury and neuroprotection. Furthermore, we report new data from our laboratory that supports the important role of peripheral cells and their interaction with the brain endothelium for the establishment of the protective phenotype in preconditioning.