Moreover, the levels of pro-inflammatory cytokines IL1-β (interleukin-1 β), interleukin-2 (IL-2), interleukin-6 (IL-6), interferon-γ (IFN-γ) and tumor necrosis factor alpha (TNF-α) are increased in the nigrostriatal dopaminergic system and peripheral nerves of PD patients [112,113,114,115,116,117]. This evidence concerns the gene TNF and Parkinson disease.