Abstract TP059: Therapeutic Post Stroke TIM1 Blockade Reduces Neuroinflammation and Improves Functional Recovery

Stroke is a leading cause of long-term disability, and post-stroke inflammation critically shapes outcomes. During the acute phase of ischemic injury, infiltrating neutrophils and T cells engage with microglia, the resident innate immune cells of the brain. While microglia initially adopt a reparative phenotype, they progressively shift toward a chronic pro-inflammatory state, driving secondary injury and impaired recovery. Strategies that suppress harmful immune activation and promote reparative phenotypes remain a major therapeutic gap. The T cell immunoglobulin and mucin domain protein TIM-1 is a type I transmembrane receptor expressed mainly on Th2 cells, where it acts as a costimulatory molecule for T cell activation. Although TIM-1 has established roles in allergy, cancer, and transplantation, its involvement in stroke is largely unexplored. Prior studies show that TIM-1 expression is transiently increased after ischemic injury, suggesting a role in post-stroke immune regulation. Methods: We used a photothrombotic stroke model in 2-month-old male mice (n=4 per condition) to test anti-TIM-1 monoclonal antibody treatment. This model induces a reproducible cortical infarct through light-activated thrombosis, enabling precise study of local immune responses. Unlike prior prophylactic studies, we used a therapeutic approach: mice received anti-TIM-1 at 400 mcg/mouse i.p. (~13.3 mg/kg; ~110 uL at 3.65 mg/mL) 1 h post-stroke, followed by a second dose at 48 h. Brains were collected 72 h after stroke for histology and immunohistochemistry. Results: Anti-TIM-1 significantly reduced infarct size. Immunostaining showed reductions in CD3+ and CD8+ T cells (adaptive infiltration), MPO+ neutrophils (innate responders), and Iba-1+ microglia (resident immune cells). Pro-inflammatory GAL-3+ microglia were also decreased. Together, these findings demonstrate that TIM-1 blockade suppresses both adaptive and innate immune activation, leading to a less inflammatory environment after stroke. Conclusions: Post-stroke administration of anti-TIM-1 mAb reduces neuroinflammation and improves outcomes in a preclinical stroke model. By modulating T cell infiltration and microglial activation, TIM-1 inhibition represents a promising immunotherapeutic strategy for stroke recovery. Our ongoing studies in humanized mouse models will determine the translational potential of anti-human TIM-1 for clinical application as a novel therapeutic strategy for stroke.