CCL2 and Alzheimer disease: According to a meta-analysis of 170 studies, patients with AD and MCI were accompanied with elevated inflammatory markers in both CSF and periphery, such as C-reactive protein (CRP), interleukin-6 (IL-6), soluble tumor necrosis factor receptor 1 (sTNFR1), soluble tumor necrosis factor receptor 2(sTNFR2), alpha1-antichymotrypsin (α1-ACT), IL-1β, soluble CD40 ligand, IL-10, monocyte chemoattractant protein-1 (MCP-1), transforming growth factor-beta 1(TGF-β1), soluble triggering receptor expressed on myeloid cells 2 (sTREM2), and so on (Shen et al., 2019).