Peripheral blood monocytes are responsible for γδ T cell activation induced by zoledronic acid through accumulation of IPP/DMAPP

Nitrogen-containing bisphosphonates indirectly activate Vγ9Vδ2 T cells through inhibition of farnesyl pyrophosphate synthase and intracellular accumulation of isopentenyl diphosphate (IPP) and dimethylallyl diphosphate (DMAPP), but the cells responsible for Vγ9Vδ2 T cell activation through IPP/DMAPP accumulation are unknown. Treatment of human peripheral blood mononuclear cells (PBMCs) with a pharmacologically relevant concentration of zoledronic acid induced accumulation of IPP/DMAPP selectively in monocytes, which correlated with efficient drug uptake by these cells. Furthermore, zoledronic acid-pulsed monocytes triggered activation of γδ T cells in a cell contact-dependent manner. These observations identify monocytes as the cell type directly affected by bisphosphonates responsible for Vγ9Vδ2 T cell activation.