Single‐Cell RNA Sequencing Identifies Accumulation of Fcgr2b + Virtual Memory‐Like CD8 T Cells With Cytotoxic and Inflammatory Potential in Aged Mouse White Adipose Tissue

ABSTRACT Aging and obesity are associated with pro‐inflammatory changes in adipose tissue. Overlapping mechanisms, such as the infiltration of inflammatory macrophages and T cells into visceral adipose tissue, have been implicated in contributing to inflammation. However, a comparative analysis of both states is needed to identify distinct regulatory targets. Here, we performed single‐cell RNA sequencing of stromal vascular fractions (SVF) isolated from gonadal white adipose tissue (gWAT) of young mice fed either a normal or a high‐fat diet, and aged mice fed a normal diet. Our analysis revealed that physiological aging, compared to high‐fat diet‐induced obesity, was associated with an accumulation of phenotypically distinct CD8 T cells resembling virtual memory (VM) CD8 T cells. These cells expressed high levels of Cd44 , Sell , Il7r , Il2rb , lacked Itga4 , and exhibited elevated Fcgr2b expression which was associated with pseudotime differentiation trajectories. Flow cytometry confirmed an age‐associated increase in Fcgr2b + CD49d‐ VM‐like CD8 T cells in gWAT. Notably, these Fcgr2b‐expressing cells exhibited a cytotoxic profile and expressed granzyme M. Functional analysis using recombinant granzyme M revealed its potential in inducing inflammation in mouse fibroblasts and macrophages. Together, our study has identified Fcgr2b + CD49d‐ VM‐like CD8 T cells in the adipose tissue of aged mice with regulatory, cytotoxic, and inflammatory potential.