Peripheral T cells can infiltrate the CNS of PD patients (Brochard et al., 2009), and interact with the α-synuclein protein, stimulating microglial activation – i.e., increase of MHC II levels – and eventually concurring to the demise of DA neurons as shown in a rat model (Subbarayan et al., 2020). The gene discussed is SNCA; the disease is Parkinson disease.