Interestingly, microglial activation and proinflammatory cytokine levels [e.g., tumor necrosis factor-α (TNF-α), interleukin (IL)-1β, and IL-6] are significantly increased in the brain, CSF, and serum of PD patients postmortem, suggesting potential roles of these markers in predicting the progression of PD (Mogi et al., 1994; Williams-Gray et al., 2016). This evidence concerns the gene IL6 and Parkinson disease.