CCL2 and Parkinson disease: While the type of assays (single vs. multiplex, platforms), assessed cytokines and cohorts’ characteristics (samples size, disease duration) are quite variable, inflammatory markers of the monocyte-macrophage signalling and chemotaxis pathway (ICAM-1, interleukin-8, MCP-1, MIP-1 beta and SCF) seem to play a relevant role in PD-associated inflammation.