Abstract WP92: Stroke Induces Long-term Central Nervous System Specific T Cell Responses

Abstract

Introduction: Stroke patients with higher lymph node antigen presentation of neuronal antigens MAP2 and NMDA receptor subunit 2A (GluN2A) exhibited smaller infarctions at day 7 and better long-term improvement at 3 months. We therefore hypothesized that T cell responses to MAP2 and GluN2A have a neuroprotective profile after stroke in mice. We previously found that stroke induced higher splenic CNS-autoreactive T cells compared to sham mice (10/12 mice vs 4/7 mice). Furthermore, CD8 T cells (10/12 mice) had higher GluN2A-specific responses compared to CD4 T cells (4/12 mice). However, it remains unclear if stroke induces long-term T cell autoimmune responses, and if these are relevant to functional recovery after stroke. Methods: Male C57BL/6 mice (B6, Jackson Labs, 8-10 weeks) were subjected to 60 mins transient middle cerebral artery occlusion. Spleens were harvested 8 and 10 days post-stroke, stained with CFSE, and cultured with GluN2A and MAP2 peptides for 6 days. Cell cultures were stained with fluorescently-tagged antibodies and quantified by flow cytometry. Another cohort of mice were euthanized 14 and 30 days after stroke, and immune cell subpopulations in the brain were quantified using flow cytometry. Results: GluN2A-15 peptide-specific CD4 (17% and 4%) and CD8 (35% and 22%) splenic T cells primarily produced pro-inflammatory cytokines TNF-α and IFN-γ, respectively. Animals with lower infarct volumes had higher number of IL-10- and TNF-α-producing neuronal antigen-specific CD4 T cells (R 2 =0.95 and R 2 =0.86) and CD8 T cells (R 2 =0.7 and R 2 =0.95) in spleen, respectively. Post-stroke mice also had higher numbers of CD4 T cells and CD8 T cells in their ischemic hemisphere compared to the contralateral hemisphere at 14 days (19-fold, p<0.0001 and 8-fold, p=0.0084) and 30 days (8-fold, p=0.0031 and 7-fold, p=0.0013) after stroke respectively. Conclusion: We previously identified GluN2A and MAP2 peptides that elicit strong positive responses from CD4 and CD8 T cells at 8 and 10 days post-stroke. We now show that there are long-term CD4 T cells and CD8 T cells responses in the ischemic hemisphere post-stroke. Future experiments will determine cytokine profile of neuronal antigen-specific cells in brain and establish if they are protective after stroke.