Blood replacement therapy improves outcomes in post-stroke mice by reducing neutrophils in the blood and MMP-9 levels in the brain and blood after stroke, decreasing infarct size and cell death, and lowering levels of post-stroke proinflammatory cytokines (IL-6, IFN-γ, and TNF-α) and chemokines (CXCL1 and CXCL2). The gene discussed is MMP9; the disease is stroke disorder.