Microglia are macrophages existing in the brain, and they become activated in response to ischemic stroke, which cause the production of ROS, cytokines (e.g., TNF-α, IL-1β, and IL-6) and chemokines (e.g., macrophage inflammatory proteins-1alpha (MIP-1α)/CCL3, monocyte chemoattractant protein-1 (MCP-1)/CCL-2 and chemokine (C-X-C motif) ligand-1 (CXCL-1)). The gene discussed is CCL2; the disease is ischemic stroke.