Post-mortem analysis of brain samples from people with PD has demonstrated increased neuronal and microglial TLR2 expression in various brain regions, including the substantia nigra and putamen [50], and increased nigrostriatal expression of TLR2-associated signalling pathways (including cluster of differentiation 14 (CD14), the co-receptor for TLR4) [51]. This evidence concerns the gene TLR4 and Parkinson disease.