Although clinical data were inconsistent for individual biomarkers and across studies, a meta-analysis included 25 studies with 2654 individuals demonstrated that PD patients had elevated levels of blood inflammatory cytokine interleukin-6 (IL-6), tumor necrosis factor-α (TNF-α), IL-1β, IL-2, IL-10, C-reactive protein (CRP) and regulated on activation, normal T cell expressed and secreted (RANTES) compared with healthy control (HC) subjects, thus clarifying the peripheral blood inflammatory cytokine profile in patients with PD (Qin et al., 2016b). Here, IL1B is linked to Parkinson disease.