CD4 and Parkinson disease: Interestingly, PRKN and LRRK2 genes that are well established to be related to familial PD11–17, were differentially expressed in CD4 and CD8 memory T cells with both genes downregulated in CD4 and upregulated in CD8 memory T cells in PD_R compared to PD_NR and HC_NR, respectively (PRKN is up in PD_R vs. PD_NR: LRRK2 is up in PD_R vs. HC_NR) indicating that the two cell types play distinct roles in PD-associated T cell autoimmunity.