Assessing the causal relationship between immune cell and Parkinson's disease by bi-directional Mendelian randomization analysis

Previous research has highlighted the significant role of immune cell features in the development and progression of Parkinson's disease (PD), though a direct causal relationship has yet to be established. In our study, we utilized genome-wide association study (GWAS) data involving 731 immune cell traits as exposure factors and GWAS data on PD as outcomes to conduct a bidirectional Mendelian randomization (MR) analysis, primarily using the inverse variance weighted (IVW) method. Our findings revealed that specific traits in classical dendritic cells (cDC), such as Myeloid dendritic cells (MDC) %DC, CD62L- DC %DC, and CD86 + MDC %DC, are positively associated with increased PD susceptibility. Similarly, B cell AC in the TBNK panel and HVEM on CD45RA- CD4 + in the Maturation stages of T cell panel also showed a heightened probability of PD. Conversely, CD45 on HLA DR + CD8br indicated a potential decrease in PD risk. This study establishes a causal link between certain circulating immune cell traits and PD, providing a foundation for further research into the immunological mechanisms of PD and potential immune therapies.