HLA-DRB1 and Parkinson disease: Because HLA-DRB1 is the most polymorphic locus in the HLA-DR region [21], we systematically analyzed the polymorphism of HLA-DRB1 alleles among sporadic PD patients and healthy controls from a Han population living in the Guangdong province of the People’s Republic of China (PRC) through polymerase chain reaction-sequencing based typing (PCR-SBT).