Objective: To investigate the influence of the peripheral immune profile in the development of cognitive impairment in PD.

Background: Dementia is frequent in advanced Parkinson’s disease (PD), while mild cognitive deficits may be present even in early to intermediate disease stages. Peripheral immunity plays a role in neurodegeneration but its influence on the development of cognitive decline in PD is still unknown

Method: Fifty PD patients (30 males; mean age at onset 68.9±8.3; mean disease duration 4.6±3.5.) were recruited.  All patients underwent a cognitive evaluation with MMSE and Addenbrooke’s cognitive examination (ACE-R). Mean MMSE score was 26.7±2.0; mean ACE-R was 85.6±8.7. The complete peripheral immune phenotype (CD4+ lymphocytes sub-populations Th1 and Th2) was examined with flow cytometry and data were retrospectively taken from a previously created database.

Results: Patients were divided in 3 groups depending on the ACE-R score (group 1:≥90; group 2:89-80; group 3:<80).  We found that age at onset was significantly higher in patients with higher compared to lower ACE-R scores. Conversely, disease duration was similar among the 3 groups. Total number (x106/L) of Th1 lymphocytes increased (group 1:96.8±79.2; group 2:101.9±52.2; group 3:107.9±59.1) and Th2 decreased (group 1:65±53.5; group 2:62.78±63; group 3:49.6±20.9) progressively from group 1 to group 3. Accordingly, expression of GATA3, normally involved in Th2 differentiation, by lymphocytes showed a postive correlation with cogntive decline (p=0.04).

Conclusion: Higher age at onset is the main risk factor for dementia in PD. Patients with a worse ACE-R score showed a predominantly pro-inflammatory peripheral immune phenotype. Immune system may indeed represent a contributing factor in the development of dementia in PD.

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MDS Abstracts - https://www.mdsabstracts.org/abstract/influence-of-peripheral-immune-system-on-cognitive-profile-in-parkinsons-disease/