Moreover, increase pro-inflammatory cytokines have been shown in human PD brain, such as IL-1β, IL-2, IL-6, EGF, and TGF-α and TGF-β in striatum (Nagatsu et al., 2000) and TNF-α upregulation in nigral microglia (Boka et al., 1994), altogether supporting a chronic pro-inflammatory milieu in the brain of PD patients. Here, TNF is linked to Parkinson disease.