Dynamics of T Lymphocyte Phenotypes Between the Periphery and the Brain From the Acute to the Chronic Phase Following Ischemic Stroke in Mice

BackgroundT lymphocytes are involved in infarct size at the early stage of stroke. However, the phenotypes of T lymphocytes and their functions in peripheral immune organs and the brain have not been well-analyzed from the acute to the chronic phase of stroke.MethodsA 45 min transient middle cerebral artery occlusion mouse model was used. The phenotypes of T lymphocytes in the thymus, spleen, blood, and brain were determined using the neurological severity score (NSS) and body weights during the 6-month follow-up. ResultsImpairment of thymocyte numbers, development, proliferation, and apoptosis was observed for up to 2 weeks. The number of mature T cells in the spleen and blood decreased and showed less interferon- production for up to 2 weeks. Increased numbers of CD44+CD62L- effector T cells and CD4-CD8-CD3+ double negative T cells were observed in mouse brains in the early phase of stroke, while interleukin (IL)-10+Foxp3+ regulatory T cell levels increased for 1 week during the chronic phase. These phenotypes were correlated with body weight and the NSS. Conclusions The recovery of T lymphocyte numbers and increased IL-10+Foxp3+ regulatory T lymphocytes may be important for the improvement of long-term neurological outcomes. Dynamic changes in T lymphocytes from the acute and chronic phase may play different roles, such as pathological and recovery roles, respectively. This study provides fundamental information regarding the T lymphocyte alterations from the brain to the peripheral immune organs from the acute to the chronic phase of stroke.