CXCL8 and Parkinson disease: The blood cells, sera, and CSF of LRRK2-associated human patients with PD have also shown abnormal expression of LRRK2 kinase and their link to elevated levels of pro-inflammatory cytokines and growth factors (e.g., IFNγ, TNFα, IL-1β, IL-2, IL-4, IL-6, IL-8, IL-10, IL-12, IL-13, GCSF, PDGF, and VEGF), loss of NCs, and the development of cognitive defects in PD (Table 2B).