Several previous studies have demonstrated that pro-inflammatory cytokines, such as TNF-α, IL-1β, IL-6 and IFN-γ, are upregulated in both cerebrospinal fluid and post-mortem brain of PD patients (Mogi et al., 1994a,b; Blum-Degen et al., 1995; Brodacki et al., 2008). Here, IFNG is linked to Parkinson disease.