Abnormalities in peripheral immune functions in patients with PD include changes in lymphocytic subpopulations in blood, deviation of T-lymphocyte subsets, impaired production of IL-2 and higher production of IFNγ by peripheral blood mononuclear cells (PBMC) that include elevation of some cytokines such as IL-2, IL1-β, IL-10, IL-4, IL-6 and TNF-α in serum or plasma [7–11]. Here, IFNG is linked to Parkinson disease.