TGF-β controls developmental fate and functional identity of thymic γδ T cells.

Gamma delta (γδ) T cells undergo a distinct developmental pathway within the thymus, where transforming growth factor β (TGF-β) exerts pivotal regulatory influence. However, the precise mechanistic contributions of TGF-β to γδ T cells differentiation and functional maturation remain incompletely understood. Here, we show that TGF-β regulates the activation state, migration capacity and inflammatory cytokine production during the development of γδ T cells in the thymus. Specifically, γδ T cells deficient in TGF-β signaling (Tgfbr1 deficient or Smad2 and Smad3 double deficient) predominantly acquired a CD44+CD45RB+ phenotype and showed impaired thymic egress, with reduced expression of CCR9, CD24, and Cxcr4. These knockout γδ T cells also exhibited elevated production of proinflammatory cytokines (interferon γ, interleukin-17A, tumor necrosis factor α) specifically in the thymus. RNA sequencing revealed that Tgfbr1-deficient γδ T cells upregulated genes associated with T cell receptor signaling, cytotoxicity, and immune activation while downregulating migration-related genes. T cell receptor repertoire sequencing further demonstrated that thymic γδ T cells lacking TGF-β signaling exhibited reduced clonal diversity accompanied by expansion of dominant clonotypes, indicating a role for TGF-β in maintaining repertoire breadth during γδ T cell development. However, we found that the differentiation of Vγ1+, Vγ4+, and Vγ7+ subsets in the thymus of the TGF-β signal-deficient mice remained largely intact. Our findings advance mechanistic understanding of γδ T cell ontogeny and underscore the role of TGF-β in balancing effector function with thymic retention or peripheral dissemination.