CCL11 and Parkinson disease: The circulating factors (e.g., serum C-C motif chemokine ligand (CCL)2, CCL11, TNF-α, IL-6, and IL-1β) are detected by microglia in the brain tissue, and microglia triggers neuronal damage, neuroinflammatory response, and CNS diseases including Alzheimer’s disease (AD), Parkinson’s disease (PD), and autism [5,6].