Structures of human γδ T cell receptor–CD3 complex

Gamma delta (γδ) T cells, a unique T cell subgroup, are crucial in various immune responses and immunopathology1-3. The γδ T cell receptor (TCR), generated by γδ T cells, recognizes a diverse range of antigens independently of the major histocompatibility complex2. The γδ TCR associates with CD3 subunits, initiating T cell activation and holding great potential in immunotherapy4. Here, we report the structures of two prototypical human Vγ9Vδ2 and Vγ5Vδ1 TCR–CD3 complexes5,6, unveiling two distinct assembly mechanisms that depend on Vγ usage. The Vγ9Vδ2 TCR–CD3 complex is monomeric, with considerable conformational flexibility in the TCRγ/TCRδ extracellular domain (ECD) and connecting peptides (CPs). The length of CPs regulates the ligand association and T cell activation. Additionally, a cholesterol-like molecule wedges into the transmembrane region, exerting an inhibitory role in TCR signaling. The Vγ5Vδ1 TCR–CD3 complex displays a dimeric architecture, where two protomers nestle back-to-back via their Vγ5 domains of TCR ECDs. Our biochemical and biophysical assays further corroborate the dimeric structure. Importantly, the dimeric form of the Vγ5Vδ1 TCR is essential for T cell activation. These findings reveal organizing principles of the γδ TCR–CD3 complex, providing insights into the γδ TCR unique properties and facilitating immunotherapeutic interventions.