Histological outcome of cerebral ischemic injury in mice lacking the transcription factor interferon regulatory factor 1 (IRF-1) gene.  Cerebral ischemia was produced by occlusion of the middle cerebral artery.  Brains were sectioned and stained with thionin.  The damage produced by cerebral ischemia is shown as the pale area marked by asterisks.  IRF-1--null mice (IRF-1^−/−^) are less damaged than wild-type mice (C57BL/6).  These data indicate that IRF-1 is involved in the molecular mechanism of ischemic brain injury.  Jerry Sedgewick is gratefully acknowledged for processing of this image.  See related article in this issue by Iadecola et al.,  pp.  719--727.