In a meta-analysis, aberrations in peripheral cytokine levels were hypothesized to be related to PD, and the authors concluded that higher peripheral concentrations of IL-6, TNFα, IL-1β, IL-2, IL-10, C-reactive protein, and RANTES in patients strengths the clinical evidence that PD is accompanied by an inflammatory response (Qin et al., 2016). This evidence concerns the gene IL2 and Parkinson disease.