Terminally differentiated effector memory T cells associate with cognitive and AD-related biomarkers in an aging-based community cohort

Abstract

Background and PurposeThe immune response changes during aging and the progression of Alzheimer’s disease (AD) and related dementia (ADRD). Terminally differentiated effector memory T cells (called TEMRA) are important during aging and AD due to their cytotoxic phenotype and association with cognitive decline. However, it is not clear if the changes seen in TEMRAsare specific to AD-related cognitive decline specifically or are more generally correlated with cognitive decline. This study aimed to examine whether TEMRAsare associated with cognition and plasma biomarkers of AD, neurodegeneration, and neuroinflammation in a community-based cohort of older adults.MethodsStudy participants from a University of Kentucky Alzheimer’s Disease Research Center (UK-ADRC) community-based cohort of aging and dementia were used to test our hypothesis. There were 84 participants, 44 women and 40 men. Participants underwent physical examination, neurological examination, medical history, cognitive testing, and blood collection to determine plasma biomarker levels (Aβ42/Aβ40 ratio, total tau, Neurofilament Light chain (Nf-L), Glial Fibrillary Acidic Protein (GFAP)) and to isolate peripheral blood mononuclear cells (PBMCs). Flow cytometry was used to analyze PBMCs from study participants for effector and memory T cell populations, including CD4+and CD8+central memory T cells (TCM), Naïve T cells, effector memory T cells (TEM), and effector memory CD45RA+T cells (TEMRA) immune cell markers.ResultsCD8+TEMRAswere positively correlated with Nf-L and GFAP. We found no significant difference in CD8+TEMRAsbased on cognitive scores and no associations between CD8+TEMRAsand AD-related biomarkers. CD4+TEMRAswere associated with cognitive impairment on the MMSE. Gender was not associated with TEMRAs, but it did show an association with other T cell populations.ConclusionThese findings suggest that the accumulation of CD8+TEMRAsmay be a response to neuronal injury (Nf-L) and neuroinflammation (GFAP) during aging or the progression of AD and ADRD. As our findings in a community-based cohort were not clinically- defined AD participants but included all ADRDs, this suggests that TEMRAsmay be associated with changes in systemic immune T cell subsets associated with the onset of pathology.