In addition, we recently observed expression of microglial Toll-like receptor-2 (TLR2), that is involved in α-synuclein-mediated microglial activation, to be different between the HC and SN of PD patients (Kim et al., 2013; Doorn et al., 2014b), consistent with the concept of region-specific microglial phenotypes in human tissue. This evidence concerns the gene TLR2 and Parkinson disease.