|Parkinsonâs disease (PD) is a progressive neurodegenerative disorder that is most common in patients over 65 years old, occurs in approximately 2 out of 1,000 people in the western hemisphere. PD is characterized by the progressive loss of midbrain dopamine neurons in the substantianigra, which causes motor dysfunction amongst other disorders. There is no cure for this disease currently, and dopamine replacement therapy has shown little efficacy. There has been growing evidence that adaptive immunity may play a role in PD progression as well as other neurodegenerative disorders including Alzheimerâs disease. In neurodegenerative diseases, the adaptive immune response may provide antigen-specific neuroprotection critical for brain repair. T cells act as the mediators of adaptive cellular immunity, allowing the body to mount increasingly potent responses to antigens of infected, transformed, or damaged self-cells with each encounter. A current debate in PD centers upon whether and how the adaptive immune response is involved in PD etiology and/or progression. Recent reports using MPTP mouse models for PD have suggested that CD4 T cells may either be protective, or promote PD-like motor behavioral symptoms.