Chuang YH, et al. - The interaction between HLA-DRB1 and smoking in Parkinson's disease (PD) underwent exploratory analysis, in three population-based case-control studies from Denmark and France. A modification was illustrated in the previously reported inverse correlation of rs660895-G with PD through smoking.This, in turn, indicated the involvement of smoking and HLA-DRB1 in the common pathways, possibly associated with neuroinflammation.