IFNAR1 and Parkinson disease: With increasing evidence of gastrointestinal dysfunction in PD patients, this study explored the contribution of the type I IFNs to the transmission of pathology from the brain to the gut in PD.<h4>Methods</h4>Young (10-12 weeks) and aged (40-50 weeks) wild-type and IFN alpha receptor (IFNAR)1<sup>-/-</sup> mice received an intrastriatal injection of human alpha-synuclein (α-syn) preformed fibrils (PFFs) (8 ug) with gut tissue analyzed 6 months postinjection.