TLR2 and Parkinson disease: The contribution of TLR2 to PD pathogenesis in human studies has also been confirmed by showing its higher expression on peripheral blood mononuclear cells (PBMCs) in the serum of PD patients compared with healthy controls [80, 86]. Furthermore, additional evidence of TLR2 involvement in PD pathogenesis in humans was obtained from a study indicating the correlation between TLR2 single nucleotide polymorphisms (SNPs) and the risk of PD development in a Chinese Han population [83].