Revisiting human circulating γδ T cells: developmental insights and manufacturing challenges for cancer immunotherapy

γδ T cells have emerged as promising candidates for adoptive cell immunotherapy due to their major histocompatibility complex-independent tumor recognition, rapid effector responses, and potential suitability for allogeneic applications. However, despite encouraging safety profiles, clinical outcomes of γδ T cell-based therapies, particularly for solid tumors, remain modest. Growing evidence suggests that both intrinsic biological heterogeneity and manufacturing-associated stress contribute to these limitations. In this review, we integrate recent advances in γδ T-cell developmental biology, immune aging, and cellular manufacturing to provide a comprehensive framework for improving therapeutic translation. We first summarize the developmental layering and functional diversification of human γδ T cells across the lifespan. We then re-analyzed publicly available single-cell RNA sequencing datasets of peripheral γδ T cells from individuals spanning adolescence to old age, revealing age-associated transcriptional remodeling linked to mitochondrial dysfunction, oxidative stress, and iron metabolism pathways. These findings provide new insights into how donor age and immune history may influence the starting cellular composition used for adoptive therapies. We further examine current ex vivo expansion strategies and highlight how repeated stimulation and prolonged culture can drive differentiation, exhaustion, and senescence-like phenotypes that limit in vivo persistence. Finally, we discuss emerging approaches, including cytokine optimization, metabolic modulation, genetic engineering, and senolytic interventions, that aim to preserve cellular fitness during manufacturing. Together, these perspectives emphasize that integrating γδ T-cell biology with aging-informed manufacturing strategies will be essential for advancing next-generation γδ T cell-based cancer immunotherapies.