CD28 superagonist-mediated boost of regulatory T cells increases thrombo-inflammation and ischemic neurodegeneration during the acute phase of experimental stroke

While the detrimental role of non-regulatory T cells in ischemic stroke is meanwhile unequivocally recognized, there are controversies about the properties of regulatory T cells (T_reg). The aim of this study was to elucidate the role of T_reg by applying superagonistic anti-CD28 antibody expansion of T_reg. Stroke outcome, thrombus formation, and brain-infiltrating cells were determined on day 1 after transient middle cerebral artery occlusion. Antibody-mediated expansion of T_reg enhanced stroke size and worsened functional outcome. Mechanistically, T_reg increased thrombus formation in the cerebral microvasculature. These findings confirm that T_reg promote thrombo-inflammatory lesion growth during the acute stage of ischemic stroke.