OBJECTIVETo investigate the dynamic changes in CD4(+)CD25(+) regulatory T cells and Foxp3 expression in peripheral blood and brain tissues of rats after acute cerebral ischemia and explore their role in the pathophysiological evolution of acute ischemic stroke.

METHODSForty-eight Wistar rats were randomized equally into ischemia and sham-operated groups, and right middle cerebral artery occlusion was induced in the former group. Flow cytometry and immunohistochemistry were employed to detect CD4(+)CD25(+) T cells and Foxp3 expression, respectively, in the peripheral blood and brain tissue at 1, 3, 7, and 14 days after modeling. The behavioral changes of the rats were evaluated using an improved NSS neurological functional scoring system.

RESULTSThe neurological function scores of the two groups both gradually declined after the operation, and showed significant differences between the two groups at all the time points of measurement (P<0.01). The CD4(+)CD25 T cells in the peripheral blood were similar between the two group at 1 and 3 days after the operation (P>0.05), but increased significantly in the ischemia group at 7 and 14 days (P<0.05) with an inverse correlation to the neurological scores (r=-0.68, P=0.01). Immunohistochemistry detected the presence of Foxp3 primarily in the ischemic region of the brain tissue 1 day after cerebral ischemia; the contralateral hemisphere also showed a small quantity of Foxp3 expression. No Foxp3 expression was detected in the brain tissue of the sham-operated group.

CONCLUSIONCD4(+)CD25 T regulatory cells participate in the inflammatory immune reactions as early as 1 day after acute cerebral ischemia in rats, which might be a protective mechanism of the brain cells.