HLA-DRB5 and Parkinson disease: In addition, PD has been associated with HLA-DRB5*01 and HLA-DRB1*15:01 MHC alleles, and the T cells of PD patients recognized α-synuclein peptides via two MHC class II beta chain alleles: HLA-DRB5*01:01 and HLA-DRB1*15:01.