Endothelial cells temporally orchestrate lymphocyte dynamics and functional outcomes after ischemic stroke

Ischemic stroke is a leading cause of death and disability worldwide. Post-stroke neuroinflammation is critically shaped by the dynamic activation and infiltration of lymphocytes, yet their precise temporal patterns, trafficking mechanisms, and ultimate impact on recovery remain poorly defined. The present study aims to define the spatiotemporal dynamics of T cells, B cells, and NK cells in peripheral and central compartments after stroke, specifically examining their migration across the cerebral vascular endothelium and their role in reshaping the brain’s immune landscape. The transient middle cerebral artery occlusion (tMCAO) model was employed. Cell adoptive transfer or antibody blockade was administrated. Integrated with bioinformatics analysis of single-cell RNA sequencing data, the neurobehavioral assessment, fluorescent-activated cell sorting (FACS), flow cytometry, RT-PCR, immunofluorescence staining and laser confocal microscopy analysis, multicolor immunohistochemistry (mIHC), and tissue loss volume measurement were performed. T, B, and NK cells exhibited divergent temporal dynamics in peripheral blood and brain infiltration following cerebral ischemia. Specifically, T cells, particularly NKT and regulatory T cells (Tregs), expanded during the subacute phase, orchestrating inflammation resolution and aiding stroke recovery. B cells mounted a rapid response, marked by a significant infiltration in the acute phase, with a distinct subset identified to facilitate white matter repair. NK cells were activated in the late phase, contributing to the reduction of brain tissue loss via immunomodulatory mechanisms. Remodeling of the cerebral vasculature post-stroke was also identified, highlighting reactive endothelial venule (REV) as a key portal for the trafficking of T, B, and NK cells into the brain parenchyma. The dynamic equilibrium of lymphocytes is a critical, stage-specific regulator of the post-stroke microenvironment, targeting REV to modulate their infiltration may constitute a key therapeutic avenue for advancing immunotherapy in ischemic stroke.