CCL2 and Parkinson disease: Accordingly, a recent systemic review and meta-analysis demonstrated significantly increased levels of IL-6, TNF-α, IL-1β, MCP-1 (monocyte chemoattractant protein 1), and CRP in both peripheral blood and CSF, as well as increased levels in IL-4, IFN-γ, STNFR1 (soluble tumor necrosis factor receptor 1), and fractalkine only in blood samples of PD patients [119].