Phosphoantigen-Driven Dissociation of Butyrophilin Oligomers Activates γδ T Cells

γδ T cells represent a promising avenue for cancer immunotherapy. The Vγ9Vδ2 T cell receptor (TCR), expressed by the predominant subset of γδ T cells, responds to phosphoantigen (pAg)-engaged butyrophilins (BTNs) on various cancer cells. Numerous preclinical and clinical trials targeting Vγ9Vδ2 TCRs and BTNs are currently underway. However, the molecular mechanism underlying pAg-mediated activation of Vγ9Vδ2 TCRs remains a subject of debate. In this study, we employed an integrative approach to elucidate the mechanism of pAg reactivity in Vγ9Vδ2 T cells. We found that BTNs form higher-order oligomers in the absence of pAg. Upon pAg binding, these oligomers dissociate into tetramers, enabling the association of the Vγ9Vδ2 TCR. This dissociation of higher-order BTN complexes is critical for pAg-mediated activation of γδ T cells. Our findings reveal a mechanism of BTN dissociation-driven pAg sensing, providing valuable insight for future immunotherapeutic strategies.