PRKN and Parkinson disease: Several genes with polymorphisms that increase the risk of neurodegenerative diseases, such as CD33 and TREM2 in AD, PRKN, SCNA, LRRK2, and HLA in PD, and C9ORF72 in ALS have been linked to various immune functions including phagocytosis, microglial activation, complement activation, MHC class II expression, and hematopoiesis (McGeer et al., 1988; Griciuc et al., 2013; Guerreiro et al., 2013; Jonsson et al., 2013; Dzamko et al., 2015; Burberry et al., 2016; Jimenez-Ferrer and Swanberg, 2018).