Role of <scp>CXCR3</scp> and <scp>CXCR6</scp> on Circulating T Cells in Patients With Parkinson's Disease

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.