[Identification of Peripheral Blood CD8 T Cells As Biomarkers of Alzheimer's Disease Based on Single-Cell Transcriptome].

Objective: Based on single-cell RNA sequencing (scRNA-seq) to explore immune characteristics in the peripheral blood of patients with Alzheimer's disease (AD) as biomarkers.

Methods: GSE168522, the scRNA-seq dataset of AD peripheral blood immune cells, was downloaded from the Gene Expression Omnibus (GEO) database and was analyzed in the RAD-Blood web server (http://www.bioinform.cn/RAD-Blood/). The changes in blood cell composition in AD patients were analyzed. The abnormal communications between different types of cells in AD patients were investigated by the CellChat R package.

Results: There were two kinds of CD8 T cells in the blood of AD patients and healthy individuals, one of which highly expressed granzyme K ( ) (false discovery rate [FDR]<0.05), and the other highly expressed , , and (FDR<0.05). In the blood of AD patients, the content of CD8 T cells was increased by 32.9% ( =5.15E-21), their interactions with other cell types were increased, and they might be associated with AD through the abnormal signal transduction of major histocompatibility complex class Ⅰ (MHC-Ⅰ). Erythrocyte provided the main ligands, that are, human leukocyte antigen (HLA) class Ⅰ molecules, including - , - , - , and - , for the abnormal MHC-Ⅰ signaling pathway of CD8 T cells. The RESISTIN signaling pathway was specifically enriched in the blood of AD patients.

Conclusion: The increased content of peripheral blood CD8 T cells, the increased interaction between CD8 T cells and erythrocytes, and the enhanced RESISTIN pathway are potential blood biomarkers of AD.