In accordance with these bacterial changes promoting an inflammatory environment in the GI system of PD patients, levels of immune factors, such as Flt1, IL-1α, and CXCL8 have been shown to be elevated in PD patient stool29, while levels of Bacteroides and Verrucomicrobia have been positively correlated with plasma levels of TNF and interferon gamma (IFNγ), respectively26. Here, IFNG is linked to Parkinson disease.