Treg depletion protects from acute ischemic stroke. (A) Infarct volumes on day 1 or day 4 after 60 minutes of tMCAO in Treg-depleted DEREG mice (DEREG + DT) and controls or Treg-depleted DEREG mice treated with anti–neutrophil serum (ANS) or control serum as calculated from TTC-stained brain sections. DT indicates diphtheria toxin (B) Neurologic deficits after stroke (day 1 or day 4) were assessed by the Bederson score and the grip test score. Consistent with infarct volume reduction, Treg-depleted DEREG mice also had a significantly better functional outcome. (C) Serial coronal MR brain images (1.5 Tesla) confirmed smaller infarct volumes in Treg-depleted DEREG mice on day 1 after 60 minutes of tMCAO and excluded secondary infarct growth in these mice until day 7. (D) Delayed depletion of Tregs in DEREG mice (DEREG + DT) also did not lead to larger infarcts on day 7 (30 minutes of tMCAO). Alleged shrinkage of strokes between day 1 and day 7 is because of fogging effects occurring during infarct maturation. *P < .05, **P < .001, and ***P < .0001 between the indicated groups; ns indicates not significant.