CyTOF profiling identifies location-specific peripheral immune checkpoint and immune cell subset in mild ischemic stroke.

Introduction: Mild ischemic stroke accounts for over half of all stroke cases, yet how peripheral immune responses evolve over time-and how they differ by infarct location-remains poorly defined. Methods: Peripheral blood was collected from ten patients with mild ischemic stroke and five matched controls at days 1, 3, and 7 after onset. Patients were stratified by cortical or subcortical infarction. High-dimensional mass cytometry was used to characterize immune cell composition and immune checkpoint expression. Results: Subcortical infarction was associated with sustained expansion of classical monocytes, persistent reduction of intermediate monocytes, and delayed PD-1/PD-L1 regulatory signaling, indicating prolonged myeloid-driven inflammation. In contrast, cortical infarction exhibited a more balanced monocyte profile and earlier PD-1 upregulation on dendritic cells and classical monocytes. CD4⁺ and CD8⁺ T-cell subsets showed distinct, location-dependent dynamics: cortical infarction induced earlier modulation of memory and regulatory phenotypes, whereas subcortical infarction produced slower but more persistent shifts. CCR5-defined CD8⁺ T-cell subsets also differed markedly, with subcortical infarction showing enrichment of CCR5⁺ effector cells, reduced checkpoint expression, and contraction of the CCR5⁻ compartment. Discussion: Peripheral immune remodeling in mild ischemic stroke displays clear infarct location-specific trajectories. These findings highlight infarct topology as a critical determinant of post-stroke immune regulation and support the development of location-adapted immunomodulatory strategies.