TLR2 and Norrie disease: The role of TLR2 as an innate immune receptor in ND has long been established.[67,68] Compared to healthy brain samples with very low TLR2 expression, autopsy analysis of brain samples from PD patients showed increased TLR2 expression in neurons and microglia in different brain regions,[69] which is consistent with the results of blood samples tested from PD and healthy patients.