Similarly, increased amounts of various inflammatory mediators (e.g., interleukin [IL]-1β, IL-6, interferon gamma [IFN-γ], and tumor necrosis factor alpha [TNF-α]) in the stool samples of patients with PD indicate the presence of gastrointestinal inflammation [64, 119, 134–136]. This evidence concerns the gene IFNG and Gastrointestinal inflammation.