Moreover, increased expression of HLA-DR is a hallmark of activated microglia, which are present in multiple neurodegenerative diseases including PD.69, 70, 71, 72 In addition, specific HLA-DRB1 variants can bind α-synuclein with high affinity, and genome-wide association studies identified HLA-DRB1 and HLA-DRA alleles to be associated with PD in different populations.73, 74, 75, 76, 77, 78 A recent study has revealed a positive correlation between LRRK2 and MHC-II levels in PD patients and a negative correlation in healthy controls.79 Here, HLA-DRB1 is linked to Parkinson disease.