T lymphocyte senescence is attenuated in Parkinson’s disease

BACKGROUND: Immune involvement is well-described in Parkinson’s disease (PD), including an adaptive T lymphocyte response. Given the increasing prevalence of Parkinson’s disease in older age, age-related dysregulation of T lymphocytes may be relevant in this disorder, and we have previously observed changes in age-associated CD8(+) T cell subsets in mid-stage PD. This study aimed to further characterise T cell immunosenescence in newly diagnosed PD patients, including shifts in CD4(+) and CD8(+) subpopulations, and changes in markers of cellular ageing in CD8(+) T lymphocytes. METHODS: Peripheral blood mononuclear cells were extracted from the blood of 61 newly diagnosed PD patients and 63 age- and sex-matched controls. Flow cytometric analysis was used for immunophenotyping of CD8(+) and CD4(+) lymphocyte subsets, and analysis of recent thymic emigrant cells. Telomere length within CD8(+) T lymphocytes was assessed, as well as the expression of the telomerase reverse transcriptase enzyme (hTERT), and the cell-ageing markers p16(INK4a) and p21(CIP1/Waf1). RESULTS: The number of CD8(+) TEMRA T cells was found to be significantly reduced in PD patients compared to controls. The expression of p16(INK4a) in CD8(+) lymphocytes was also lower in patients versus controls. Chronic latent CMV infection was associated with increased senescent CD8(+) lymphocytes in healthy controls, but this shift was less apparent in PD patients. CONCLUSIONS: Taken together, our data demonstrate a reduction in CD8(+) T cell replicative senescence which is present at the earliest stages of Parkinson’s disease. SUPPLEMENTARY INFORMATION: The online version contains supplementary material available at 10.1186/s12974-021-02287-9.