HDMAPP is a metabolite of the microbial dioxyxylulose-phosphate pathway, which is analogous to the isopentenyl pyrophosphate pathway in mammals. It is a protease-resistant and phosphatase-sensitive pyrophosphate produced by bacteria and plants. HDMAPP is a non-peptide ligand, also called a phosphoantigen, that binds the T cell receptor on Vγ9Vδ2 peripheral blood lymphocytes with high affinity (EC50 = 0.39 nM). It induces the expansion of human memory Vγ9Vδ2 T cells, but does not increase their ability to inhibit intracellular mycobacterial growth. Neonatal Vγ9Vδ2 T cells require micromolar concentrations of HDMAPP to drive expansion.
