Fitness Training for γδ T cells in mouse and human atherosclerosis takes place in plaques and artery tertiary lymphoid organs

γδ T cells represent a heterogeneous family of innate-like lymphocytes with adaptive immunity features. Although abundant in barrier tissues such as skin and intestine, γδ T cells are rare in the cardiovascular system, which severely limits exploration of their roles in atherosclerosis. Consequently, the spatial localization, functional states, and antigen-driven responses of γδ T cells within atherosclerotic lesions remain poorly defined. To nevertheless examine γδ T cells in atherosclerosis, we employed an integrative, three-pronged strategy combining γδ T cell single-cell RNA sequencing (scRNA-seq) and single-cell T cell receptor sequencing (scTCR-seq), spatial transcriptomics, and large-scale multi-dataset scRNA-seq integration across multiple hyperlipidemic mouse models. Large-scale multi-dataset scRNA-seq integration was also applied to human atherosclerotic plaque datasets. We found significant enrichment of γδ T cells within both atherosclerotic plaques and artery tertiary lymphoid organs (ATLOs), particularly of the proinflammatory IL17-producing γδ T17 subtype. Unexpectedly, γδ T17 cells containing paired Vγ6Vδ4 TCR chains with identical complementarity-determining region 3 (CDR3) sequences underwent clonal expansion in atherosclerotic plaques and ATLOs. Transcriptomic analysis revealed that plaques and ATLOs locally educate γδ T17 cells - here termed γδ eduT17 cells - towards an anti-apoptotic, tissue-resident, and apparent hypofunctional phenotype. Furthermore, γδ eduT17 cells underwent metabolic reprogramming within the atherosclerotic microenvironment. Spatial transcriptomics revealed that γδ T cells preferentially localize in ATLOs, particularly at the interface between T cell zones and B cell follicles. Multi-dataset integration confirmed the conservation of these features across multiple hyperlipidemic mouse models. In contrast, human atherosclerotic plaques harbored substantially fewer γδ T cells and the human phenotypes were dominated by an effector/cytolytic γδ T cell subtype, characterized by transcriptomes enriched in cytotoxic effector molecules. Our findings identify γδ T cells as a previously underappreciated T cell lineage population in atherosclerosis. Murine atherosclerosis is characterized by the enrichment, education, and clonal expansion of proinflammatory γδ eduT17 cells within plaques and ATLOs. In contrast, human plaques harbor γδ T cells with cytolytic features, suggesting divergent roles of γδ T cells between species. These results highlight the importance of local vascular microenvironments in shaping γδ T cell function and emphasize the need for caution when extrapolating mechanistic insights from mouse models to human atherosclerosis.