Essential requirements of zoledronate-induced cytokine and γδ T cell proliferative responses

J Immunol. 2013 Aug 1;191(3):1346-55. doi: 10.4049/jimmunol.1300603. Epub 2013 Jun 21.


The potent nitrogen-containing bisphosphonate zoledronate inhibits farnesyl pyrophosphate synthase, a key enzyme of the mevalonate pathway that is often hyperactive in malignant cells. Zoledronate activates human Vγ9Vδ2 T cells, which are immune sentinels of cell stress and tumors, through upstream accumulation of the cognate Ag isopentenyl pyrophosphate. IL-18 was shown to enhance zoledronate-induced γδ T cell activation. Although monocytes have been considered important accessory cells that provide the Ag isopentenyl pyrophosphate, CD56(bright)CD11c(+) NK cells were postulated to mediate the costimulatory effects of IL-18. We report in this article that downstream depletion of geranylgeranyl pyrophosphate (GGPP), which is required for protein prenylation, caused cell stress in monocytes, followed by caspase-1-mediated maturation and release of IL-18, which, in turn, induced γδ T cell CCL2. Likewise, zoledronate caused a substantial delay in γδ T cell expansion, which could be skipped by GGPP supplementation. Moreover, repletion of GGPP, which prevented acute zoledronate toxicity, and supplementation with IL-18, which strongly upregulated IL-2Rα (CD25) and favored the central memory phenotype, were sufficient to enable zoledronate-induced expansion of highly purified γδ T cells, even when starting cell numbers were as low as 10(4) γδ T cells. Our study reveals essential components of γδ T cell activation and indicates that exogenous IL-18, which can directly costimulate γδ T cells, eliminates the need for any accessory cells. Our findings will facilitate the generation of robust γδ T cells from small blood or tissue samples for cancer immunotherapy and immune-monitoring purposes.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Bone Density Conservation Agents / pharmacology*
  • Caspase 1 / metabolism
  • Cell Proliferation / drug effects
  • Cells, Cultured
  • Chemokine CCL2 / biosynthesis
  • Diphosphonates / pharmacology*
  • Humans
  • Imidazoles / pharmacology*
  • Interleukin-18 / biosynthesis
  • Interleukin-18 / metabolism
  • Interleukin-18 / pharmacology*
  • Interleukin-2 Receptor alpha Subunit / biosynthesis
  • Leukocytes, Mononuclear / metabolism
  • Lymphocyte Activation / drug effects
  • Lymphocyte Activation / immunology
  • Polyisoprenyl Phosphates / metabolism
  • Polyisoprenyl Phosphates / pharmacology
  • Receptors, Antigen, T-Cell, gamma-delta / immunology*
  • T-Lymphocytes / drug effects*
  • T-Lymphocytes / immunology
  • Zoledronic Acid


  • Bone Density Conservation Agents
  • CCL2 protein, human
  • Chemokine CCL2
  • Diphosphonates
  • Imidazoles
  • Interleukin-18
  • Interleukin-2 Receptor alpha Subunit
  • Polyisoprenyl Phosphates
  • Receptors, Antigen, T-Cell, gamma-delta
  • Zoledronic Acid
  • Caspase 1
  • geranylgeranyl pyrophosphate