Butyrophilin 3A1 (BTN3A1) is an integral membrane protein capable of detecting phosphoantigens, like (E)-4-hydroxy-3-methyl-but-2-enyl diphosphate (HMBPP), through its internal B30.2 domain. Detection of phosphoantigens leads to interactions with butyrophilin 2A1 and the subsequent activation of γδ-T cells. Though crystallography and functional assays have been crucial for determining vital residues of the BTN3A1/HMBPP/BTN2A1 complex, the mechanism for signal transduction is still unclear. Here, we utilize