# Role of CXCR3 and CXCR6 on Circulating T Cells in Patients With Parkinson's Disease

## TL;DR

This study explores how CXCR3 and CXCR6 on T cells differ in Parkinson's disease patients and their link to inflammation.

## Contribution

The study reveals altered CXCR3 and CXCR6 expression on CD8+ T cells in Parkinson's disease without a link to peripheral inflammation.

## Key findings

- CD8+ T cells are significantly reduced in Parkinson's disease patients compared to healthy controls.
- CXCR3 and CXCR6 expression is elevated on CD8+ T cells in Parkinson's disease patients.
- No significant correlation was found between CXCR3/CXCR6 expression and peripheral inflammation markers in Parkinson's disease.

## Abstract

Immune dysregulation is involved in Parkinson's disease (PD), but the roles of C‐X‐C motif chemokine receptor 3 (CXCR3)/chemokine receptor 6 (CXCR6) on T cells and their correlation with peripheral inflammation remain unclear. This study investigated their expression on peripheral blood T cells and correlation with inflammation in PD. A total of 36 PD patients and 26 healthy controls were enrolled; their clinical information and laboratory test results (including the systemic immunoinflammatory index [SII], neutrophil‐to‐lymphocyte ratio [NLR], monocyte‐to‐lymphocyte ratio [MLR], platelet‐to‐lymphocyte ratio [PLR], monocyte‐to‐high‐density lipoprotein ratio [MHR], and erythrocyte distribution width over platelets ratio [RPR]) were recorded. Meanwhile, a multicolour flow cytometry protocol using six cell surface antibodies (CD3, CD4, CD8, CD45RO, CXCR3, and CXCR6) was applied. The results showed that CD8+ T cells were significantly reduced in the PD group compared with healthy controls (p < 0.001), and CXCR3 expression was significantly increased on peripheral blood CD4+ effector T cells and CD8+ T cells of PD patients (p < 0.001). Additionally, CXCR6 expression was significantly elevated on cytotoxic T lymphocytes (CTLs) (p < 0.0001) but showed no significant difference on CD4+ T cells between PD patients and controls (p > 0.05). Compared with healthy controls, PD patients had significantly increased peripheral blood C‐reactive protein (CRP) levels (p < 0.001) but remarkably decreased monocytes, lymphocytes, and MHR (p < 0.01). Collectively, the upregulated expression of CXCR3 and CXCR6 predominantly on CD8+ T lymphocytes may contribute to PD pathogenesis, though no significant correlation between the expression of these receptors and peripheral inflammation was observed.

CXCR3 and CXCR6 expression may be dependent on CD8+ T lymphocytes to participate in the pathogenesis of PD, while has no effects on peripheral inflammation.