RORγt+ c-Maf+ Vγ4+ γδ T cells are generated in the adult thymus but do not reach the periphery

Targeting T-cell Aging to Remodel the Aging Immune System and Revitalize Geriatric Immunotherapy

The aging immune system presents profound challenges, notably through the decline of T cell function, which is critical for effective immune responses. As age-related changes lead to diminished T cell diversity and heighten immunosuppressive environments, older individuals face increased susceptibility to infections, autoimmune diseases, and reduced efficacy of immunotherapies. This review investigates the intricate mechanisms by which T cell aging drives immunosenescence, including immune suppression, immune evasion, reduced antigen reactivity, and the overexpression of immune checkpoint molecules. By delving into innovative therapeutic strategies aimed at rejuvenating T cell populations and modifying the immunological landscape, we highlight the potential for enhancing immune resilience in the elderly. Ultimately, our goal is to outline actionable pathways for restoring immune function, thereby improving health outcomes for aging individuals facing immunological decline.

Signature cytokine-associated transcriptome analysis of effector γδ T cells identifies subset-specific regulators of peripheral activation

γδ T cells producing either interleukin-17A (γδ17 cells) or interferon-γ (γδIFN cells) are generated in the mouse thymus, but the molecular regulators of their peripheral functions are not fully characterized. Here we established an Il17a-GFP:Ifng-YFP double-reporter mouse strain to analyze at unprecedented depth the transcriptomes of pure γδ17 cell versus γδIFN cell populations from peripheral lymph nodes. Within a very high fraction of differentially expressed genes, we identify a panel of 20 new signature genes in steady-state γδ17 cells versus γδIFN cells, which we further validate in models of experimental autoimmune encephalomyelitis and cerebral malaria, respectively. Among the signature genes, we show that the co-receptor CD6 and the signaling protein Themis promote the activation and proliferation of peripheral γδIFN cells in response to T cell antigen receptor stimulation in vitro and to Plasmodium infection in vivo. This resource can help to understand the distinct activities of effector γδ T cell subsets in pathophysiology.

IL-27 maintains cytotoxic Ly6C+ γδ T cells that arise from immature precursors

In mice, γδ-T lymphocytes that express the co-stimulatory molecule, CD27, are committed to the IFNγ-producing lineage during thymic development. In the periphery, these cells play a critical role in host defense and anti-tumor immunity. Unlike αβ-T cells that rely on MHC-presented peptides to drive their terminal differentiation, it is unclear whether MHC-unrestricted γδ-T cells undergo further functional maturation after exiting the thymus. Here, we provide evidence of phenotypic and functional diversity within peripheral IFNγ-producing γδ T cells. We found that CD27+ Ly6C- cells convert into CD27+Ly6C+ cells, and these CD27+Ly6C+ cells control cancer progression in mice, while the CD27+Ly6C- cells cannot. The gene signatures of these two subsets were highly analogous to human immature and mature γδ-T cells, indicative of conservation across species. We show that IL-27 supports the cytotoxic phenotype and function of mouse CD27+Ly6C+ cells and human Vδ2+ cells, while IL-27 is dispensable for mouse CD27+Ly6C- cell and human Vδ1+ cell functions. These data reveal increased complexity within IFNγ-producing γδ-T cells, comprising immature and terminally differentiated subsets, that offer new insights into unconventional T-cell biology.

Unraveling the secrets of γδ T cells with single-cell biology

Recent technological advancements have enabled us to study the molecular features of cellular states at the single-cell level, providing unprecedented resolution for comprehending the identity and function of a cell. By applying these techniques across multiple time frames, tissues, and diseases, we can delve deeper into the mechanisms governing the development and functions of cell lineages. In this review, I focus on γδ T cells, which are a unique and functionally nonredundant T cell lineage categorized under the umbrella of unconventional T cells. I discuss how single-cell biology is providing unique insights into their development and functions. Furthermore, I explore how single-cell methods can be used to answer several key questions about their biology. These investigations will be essential to fully understand their translational potential, including their role in cytotoxicity and tissue repair in cancer and regeneration.

PRDM16 regulates γδT17 cell differentiation via controlling type 17 program and lipid-dependent cell fitness

γδT17 cells are a subset of γδT cells producing IL-17, which is crucial for protection against bacterial and fungal infections. It has recently been shown that γδT17 cells have enriched lipid storage and lipid metabolism. However, the regulation of γδT17 cell function and differentiation with respect to lipids remains unknown. Here, we report that PRDM16 is a critical regulator of γδT17 cell differentiation, controlling type 17 immunity gene expression program and lipid-dependent cell fitness. We demonstrated that γδT17 cells have higher lipid-dependent cell fitness, which is negatively correlated with the expression of Prdm16. Loss of Prdm16 enhances the function and differentiation of γδT17 cells, and increases their fitness in lipid-rich environments. Specifically, loss of Prdm16 exacerbates development of psoriasis in the skin, a lipid-rich organ, and Prdm16 controls lipid-mediated differentiation of Vγ4+ γδT17 cells, which are the major source of IL-17 during the onset of psoriasis. Our study highlights the potential impact of PRDM16 on lipid-dependent fitness and protective immune function of γδT cells and also on the immunotherapy of psoriasis and inflammatory diseases.