This indicates that until 1 week after ischemic stroke, PDGFRβ+ cells at the lesion site, which is located between the striatum and overlaying cortex, are mainly reactive pericytes and that PDGFRα+ cells constitute a distinct population of reactive cells, yet that intimately interacts with reactive PDGFRβ+ cells. The gene discussed is PDGFRB; the disease is ischemic stroke.