IFNG and Parkinson disease: Studies of colon biopsies have shown that the level of expression of inflammatory markers, including toll-like receptor (TLR)-2, TLR4, CD3+ T cells, T helper (Th)1, Th17, and related pro-inflammatory cytokines and chemokines CCL2, CCL5, CCR5, IL-1ß, IL-6, IL-8, IL-17A, interferon (IFN)-ß, IFN-γ, TNF-α associated with glial cell markers is elevated in PD patients compared to controls [28, 66].