IL-12 alone and in synergy with IL-18 inhibits osteoclast formation in vitro.
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.
Horwood
N J
NJ
St. Vincent's Institute of Medical Research, Fitzroy, Victoria, Australia.
Elliott
J
J
Martin
T J
TJ
Gillespie
M T
MT
D000818:Animals; D018929:Cell Culture Techniques / Q000295:instrumentation / Q000379:methods; D002454:Cell Differentiation / Q000276:immunology; D002460:Cell Line; D002478:Cells, Cultured; D018920:Coculture Techniques; D015536:Down-Regulation / Q000276:immunology; D004338:Drug Combinations; D004357:Drug Synergism; D016178:Granulocyte-Macrophage Colony-Stimulating Factor / Q000378:metabolism / Q000502:physiology; D006131:Growth Inhibitors / Q000378:metabolism / Q000502:physiology*; D007371:Interferon-gamma / Q000378:metabolism / Q000502:physiology; D018664:Interleukin-12 / Q000378:metabolism / Q000502:physiology*; D020382:Interleukin-18 / Q000378:metabolism / Q000502:physiology*; D008297:Male; D051379:Mice; D008810:Mice, Inbred C57BL; D018345:Mice, Knockout; D010010:Osteoclasts / Q000166:cytology* / Q000276:immunology*; D016187:Receptors, Granulocyte-Macrophage Colony-Stimulating Factor / Q000172:deficiency / Q000235:genetics; D017471:Receptors, Interferon / Q000172:deficiency / Q000235:genetics; D013601:T-Lymphocytes / Q000276:immunology / Q000378:metabolism; D000096743:Interferon gamma Receptor
D004338:Drug Combinations; D016178:Granulocyte-Macrophage Colony-Stimulating Factor; D006131:Growth Inhibitors; D007371:Interferon-gamma; D018664:Interleukin-12; D020382:Interleukin-18; D016187:Receptors, Granulocyte-Macrophage Colony-Stimulating Factor; D017471:Receptors, Interferon; D000096743:Interferon gamma Receptor