All animal experiments were approved by the University of Pittsburgh Institutional Animal Care and Use Committee and performed in accordance with the principles outlined in the National Institutes of Health Guide for the Care and Use of Laboratory Animals. Wild-type (WT) or IL-4 knockout (KO) male C57/BL6 mice (8–10w, 25–30 g body weight; Jackson Laboratory, Bar Harbor, Maine, USA) were randomly assigned to sham or cerebral ischemia groups using a lottery drawing box. Transient focal ischemia was induced by MCAO for 60 minutes as previously described.2 Sham-operated animals underwent anesthesia and exposure of the arteries without MCAO induction. Rectal temperature was maintained at 37.0°C±0.5°C during and after surgery with a temperature-controlled heating pad. Physiological parameters were maintained within normal ranges. Regional cerebral blood flow (rCBF) was monitored in all stroke animals using laser Doppler flowmetry. Animals that died or failed to show at least 70% rCBF reduction were excluded from further analyses. Mice in both genotypes were subjected to repeated measurements of CBF before ischemia, 5 min after tMCAO, and 5 min after reperfusion using a laser speckle contrast imager (LDF, PeriFlux System 5000, Perimed). In all experiments, the tMCAO or sham surgeries were performed by an investigator blinded to genotype.