C1R and Parkinson disease: These results show that the plasma-derived exosome proteins; clusterin, complement C1r subcomponent, and apolipoprotein A1, and the fibrinogen gamma chain, are potential biomarker candidates for PD diagnosis, and exosomal apolipoprotein A1 can be used as a biomarker for tracking PD progression (Kitamura et al., 2018).