IL-12 alone and in synergy with IL-18 inhibits osteoclast formation in vitro

Nicole J. Horwood, Jan Elliott, T. John Martin, Matthew T. Gillespie

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IL-12, like IL-18, was shown to potently inhibit osteoclast formation in cultures of cocultures of murine osteoblast and spleen cells, as well as in adult spleen cells treated with M-CSF and receptor activator of NF-kappaB ligand (RANKL). Neither IL-12 nor IL-18 was able to inhibit RANKL-induced osteoclast formation in cultured RAW264.7 cells, demonstrating that IL-12, like IL-18, was unable to act directly on osteoclastic precursors. IL-12, like IL-18, was found to act by T cells, since depletion of T cells from the adult spleen cell cultures ablated the inhibitory action of IL-12 and addition of either CD4 or CD8 T cells from C57BL/6 mice to RANKL-stimulated RAW264.7 cultures permitted IL-12 or IL-18 to be inhibitory. Additionally, IL-12 was still able to inhibit osteoclast formation in cocultures with osteoblasts and spleen cells from either GM-CSF R(-/-) mice or IFN-gamma R(-/-) mice, indicating that neither GM-CSF nor IFN-gamma was mediating osteoclast inhibition in these cultures. Combined, IL-18 and IL-12 synergistically inhibited osteoclast formation at concentrations 20- to 1000-fold less, respectively, than when added individually. A candidate inhibitor could not be demonstrated using neutralizing Abs to IL-4, IL-10, or IL-13 or from mRNA expression profiles among known cytokine inhibitors of osteoclastogenesis in response to IL-12 and IL-18 treatment, although the unknown inhibitory molecule was determined to be secreted from T cells.

Original languageEnglish
Pages (from-to)4915-4921
Number of pages7
JournalJournal of Immunology
Issue number8
Publication statusPublished - 15 Apr 2001


  • Animals
  • Cell Culture Techniques/instrumentation
  • Cell Differentiation/immunology
  • Cell Line
  • Cells, Cultured
  • Coculture Techniques
  • Down-Regulation/immunology
  • Drug Combinations
  • Drug Synergism
  • Granulocyte-Macrophage Colony-Stimulating Factor/metabolism
  • Growth Inhibitors/metabolism
  • Interferon-gamma/metabolism
  • Interleukin-12/metabolism
  • Interleukin-18/metabolism
  • Male
  • Mice
  • Mice, Inbred C57BL
  • Mice, Knockout
  • Osteoclasts/cytology
  • Receptors, Granulocyte-Macrophage Colony-Stimulating Factor/deficiency
  • Receptors, Interferon/deficiency
  • T-Lymphocytes/immunology

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