MAPT and Parkinson disease: However, the two ND pathologies investigated are highly complex, and MGB-immune cell interactions can be differently regulated; indeed, in PD patients, α-syn is the main protein involved in CNS accumulation, but it can also be found in the gastrointestinal tract nerve plexuses, while in AD pathogenesis in the CNS, there is an accumulation of extracellular Aβ peptide and intracellular NFTs composed of hyperphosphorylated tau protein.