Astrocyte-derived interleukin-15 exacerbates ischemic brain injury via propagation of cellular immunity

Significance Ischemic stroke is a leading cause of death and disability worldwide. Evidence indicates the detrimental effects of lymphocyte infiltration into the ischemic brain. However, a knowledge gap exists relating to the brain-specific cellular constituents and environmental factors that dictate the phenotype and function of infiltrating lymphocytes. Astrocytes bridge interactions between ischemic neurons and lymphocytes. We show that brain ischemia induces robust up-regulation of astrocytic interleukin-15 (IL-15). The present study was directed toward understanding the role of astrocyte-derived factors such as IL-15 in stroke. We discovered that astrocytic IL-15 is necessary and sufficient to amplify cell-mediated immune responses that promote ischemic brain injury. These results provide definitive evidence on the role of astrocyte-derived IL-15 in ischemic brain injury.