Previous reports established certain secreted cytokines as reliable biomarkers in serum and plasma of PD patients, among them IL-1β, IL-18, IL-6, IL-10, IL-8, TNF-α (Nagatsu et al., 2000; Brodacki et al., 2008; Qin et al., 2016). Here, CXCL8 is linked to Parkinson disease.