Peripheral Immunological Signatures of Parkinsonism: Insights from the Caribbean vs. North America

The contribution of the peripheral immune system to Parkinson's disease (PD) and Atypical parkinsonism (AP), including multiple system atrophy, progressive supranuclear palsy, and Caribbean atypical parkinsonism, is increasingly recognized, albeit incompletely resolved. Our study aimed to compare the peripheral immunological profile of PD and AP patients from two distinct geographical areas, Guadeloupe and Montreal. We conducted a cross-sectional study on PD and AP patients and healthy controls from Guadeloupe and Montreal (total 57 subjects). We collected clinical assessments and arbovirus serologies. We performed an immune profiling of peripheral blood mononuclear cells by flow cytometry. Nearly all Guadeloupe subjects had prior exposure to an endemic arbovirus, while seropositivity was minimal in Montreal. Samples from the Guadeloupe cohort showed an increased proportion of γδ T cells and enhanced CD8⁺ T cell inflammatory properties, particularly in PD patients and healthy controls, compared to their Montreal counterparts. Specific memory B cell subsets were more abundant in Guadeloupe-PD and Guadeloupe-AP than in Montreal patients. The percentage of plasmablasts positively correlated with clinical scores in Guadeloupe-PD and AP patient groups. Montreal-AP patients displayed elevated monocyte percentages; proportions of monocytes and classical monocytes correlated with clinical scores in this patient group. Our study highlights immune differences related to disease type (PD vs. AP) and geographical location (Guadeloupe vs. Montreal), particularly in AP patients. A better understanding of the impact of environmental factors and age-related changes on the peripheral immune system of PD and AP patients could provide essential information to slow down and treat these conditions.