CCL2 and nervous system disorder: In the aged brain, monocytes may have a greater capacity to infiltrate the brain on the brain‐blood barrier (BBB) during injury or neurological disorders.[56] Particularly, animal experiments showed that aged mice harbor expanded CCR2+ monocytes postinjury/chronic inflammation that can infiltrate the brain based on MCP1/CCR2 chemotaxis signaling.[57] Postinfiltration, monocytes may induce proinflammatory responses in neighboring glial cells such as astrocytes.