There is evidence for activation of both innate and adaptive immune system mechanisms in PD: HLA-DR reactive microglia surround areas of α-syn pathology in postmortem brain tissue, CD4 and CD8 T cell infiltration into the brain are observed, and pro-inflammatory cytokines are increased in blood and cerebrospinal fluid (CSF) of PD patients [6–9]. This evidence concerns the gene CD8A and Parkinson disease.