Microbe-derived hydroxymethyl-but-2-enyl-pyrophosphate (HMBPP) is ~10,000-fold more potent than cancer cell-derived IPP in the activation of Vγ9Vδ2 T cells (18), but it is not understood how HMBPP triggers stronger signaling in Vγ9Vδ2 T cells than IPP. Here, IPP is linked to cancer.