Better begins with different: Navigating the diversity of the γ9δ2T cell receptors, phenotypes and functions

This thesis explores the biology and therapeutic potential of human gamma delta T cells (γδ T cells) and their T cell receptors (TCRs), in particular of the subset which expresses the Vγ9Vδ2 TCR. Despite being uniformly triggered by nonpolymorphic butyrophilin proteins (BTNs) on the surface of the target tissue, Vγ9Vδ2 TCRs nevertheless display a repertoire with striking complemetarity region 3 (CDR3) diversity. This thesis provides the biological rationale for this diversity by showing that Vγ9Vδ2 TCR repertoire harbors a range of ligand-binding affinities. Variation in Vγ9Vδ2 TCR affinity translates into graded inflammatory responses when applied through T cell and molecular engineering strategies, including T cells engineered to express defined γδ TCRs (TEGs) and γδ TCR anti-CD3 bispecific molecules (GABs). Both platforms outperform unmodified γδT cells in anti-tumor activity when equipped with high-affinity TCRs.
Layered upon TCR diversity is the heterogeneity in phenotypes, transcriptomes, and effector functions of Vγ9Vδ2 TCR–expressing T cells. This additional level of diversity seen in ex vivo and cultured γ9δ2 T cells is the further focus of this thesis, which links specific phenotypic features, transcriptomic profiles, and effector functions to TCR affinity by demonstrating TCR-dependent biases across these characteristics, with direct implications for the design of γδ T cell– and Vγ9Vδ2 TCR–based immunotherapies.
Lastly, this thesis adds mechanistic insight into Vγ9Vδ2 TCR–ligand interaction framework by identifying Ras homolog gene family member B (RhoB) as an intracellular regulator of BTN membrane organization and conformation, and by demonstrating that Vγ9Vδ2 TCR–mediated targeting of specific tumors is RhoB-dependent.