Journal of Parkinson's diseaseOct 8, 2026

Overview of immune cells in the blood of people with Parkinson’s disease

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Updated Oct 9, 2026

Abstract

A steady expansion of peripheral immune cell research in Parkinson's disease (PD) has been observed, particularly over the last decade.

Deep immunophenotyping identifies common immune signatures in PD, showing increased pro-inflammatory T-cell subsets and altered monocyte distributions.
Findings include a rise in cytotoxic natural killer cells and a higher neutrophil-to-lymphocyte ratio.
Dysregulated immune pathways related to activation, cell movement, mitochondrial function, and autophagy-lysosomal processes are associated with PD.
Stimulation-based tests indicate a consistent hyper-responsiveness of T-cells in PD, while responses of myeloid cells vary based on context.
Significant variability and under-reporting in study designs limit the ability to draw strong conclusions about peripheral immunity in PD.

Simplified

Parkinson's disease (PD) is increasingly recognized as a multi-system disorder with immune dysregulation extending beyond the central nervous system. Although numerous studies have examined peripheral immune alterations in people with PD, findings remain heterogeneous and difficult to reconcile. To clarify the current landscape, we conducted a comprehensive scoping review of human studies profiling peripheral blood immune cells in PD. Following PRISMA-ScR guidelines, we systematically screened the literature and curated studies reporting in vivo and ex vivo immune characterizations from PD patients. Eligible studies based on pre-defined criteria were assessed for patient demographics and clinical variables, experimental and analytical approaches, and reported immune outcomes. Our synthesis reveals a steady expansion and diversification of peripheral immune cell research in PD especially over the last decade. Deep immunophenotyping identifies convergent signatures across in vivo studies of both innate and adaptive compartments, including expanded pro-inflammatory T-cell subsets, altered monocyte subset distributions, increased cytotoxic natural killer cells and neutrophil-to-lymphocyte ratio, and dysregulated pathways related to immune activation, chemotaxis, mitochondrial function, and autophagy-lysosomal processes. Stimulation-based ex vivo assays further demonstrate recurrent T-cell hyper-responsiveness in PD, whereas myeloid cell responses are more variable and context dependent. Critically, this review highlights substantial variability and under-reporting in study design, which impeded our ability to make strong conclusions relating to many aspects of PD peripheral immunity.

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Overview of immune cells in the blood of people with Parkinson’s disease

Abstract

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