Production Of Osteoclast Activating Factors Research Articles

Induction of bone resorbing activity by normal and rheumatoid arthritis T cells

We studied the role of T cells in the production of osteoclast activating factor (OAF) using anti-CD3 MAb as a specific T cell activator. OAF activity was totally inhibited by anti-IL-1β. Peripheral blood mononuclear cells (PBMNC) from normal subjects produced more OAF than did PBMNC from rheumatoid arthritis (RA) patients. Mononuclear cells (MNC) from RA synovial fluid produced less OAF than did RA peripheral blood. We conclude that (i) specific T cell stimulation induces OAF production which may be attributed to interleukin 1 (IL-1) activity, (ii) the inhibition by anti-IL-1β of OAF production following anti-CD3 stimulation suggests that the T cell signal is being transmitted to the macrophage, and (iii) RA MNC are deficient in T cell-mediated OAF production.

Production of human/mouse hybridomas secreting a human lymphokine, osteoclast activating factor

A human/mouse hybridoma was developed which has the property of secreting a human bone resorbing factor similar or identical to the osteoclast activating factor (OAF) isolated from human tonsil lymphocytes. Mouse plasmacytoma cells negative for OAF production were fused with an enriched subpopulation of human tonsil lymphocytes that had been activated with phytohemagglutinin (PHA) to produce OAF (G. E. Nedwin, M. A. Mohler, and R. A. Luben, submitted for publication). Culture supernatants from mixed hybridomas contained a bone resorbing protein shown to cause the release of 45Ca from previously labeled mouse calvaria. The bone resorbing activity from these hybridomas was inhibited by the presence of OAF-specific monoclonal antibodies. Several hybridomas retained OAF production following limited dilution cloning. One clone, CD6.20, showed a biphasic dose-response curve for bone resorption similar to that of purified OAF from PHA-activated human tonsil lymphocytes. OAF production in the CD6.20 cell line has been retained for over 100 passages. Karyotype analysis of this cell shows the presence of human chromosomes 10 and 18 and the X chromosome.

Relation of osteoclast activating factor production to extent of bone disease in multiple myeloma.

Measurements of total body myeloma cell number and osteoclast activating factor (OAF) production by bone marrow myeloma cells in vitro were made in 33 patients with plasma cell myeloma. There was a highly significant correlation (P < 0.001) between the amount of OAF produced by bone marrow myeloma cells and the extent of skeletal destruction. Serial studies indicated reduction of OAF production with remission induction and high OAF production at the time of relapse with new bone destruction. Although hypercalcaemia occurred only in patients with the most extensive bone lesions, there was no direct relationship between OAF production and the serum calcium concentration. These data suggest that measurement of OAF production in multiple myeloma may predict those patients at risk for development of extensive skeletal destruction due to this neoplasm.

Monocytes regulate osteoclast-activating factor production by releasing prostaglandins.

Osteoclast-activating factor (OAF), a powerful stimulator of osteoclastic bone resorption, is released by peripheral blood mononuclear cells on exposure to phytohemagglutinin (PHA) or a specific antigen to which the leukocytes have been previously exposed. Both lymphocytes and monocytes are required in the leukocyte population for OAF release to occur. In this study we examined the relationship between the lymphocyte and monocyte in OAF production. Biological activity, as a result of OAF, was assessed by a bioassay based on the release of previously incorporated 45Ca from fetal rodent long bones in organ culture. We found that an enriched lymphocyte population depleted of monocytes by serial adherence does not release OAF after stimulation with PHA, although the cells are activated as assessed by [3H]thymidine and 3H-amino acid incorporation. When conditioned media harvested from adherent cells which did not contain OAF was added to the enriched lymphocytes, OAF release occurred. Media harvested from adherent cells which were cultured with indomethacin (10 microM), an inhibitor of prostaglandin synthesis, did not permit OAF release by activated lymphocytes. When PGE1 and PGE2 (0.1 microM) were added exogenously to the enriched lymphocyte population, OAF release occurred after stimulation with PHA. These results indicate that, (a) the activated lymphocyte is the cell or origin of OAF, (b) prostaglandins produced by monocytes are necessary for OAF production by activated lymphocytes, and (c) monocyte prostaglandins can influence bone resorption indirectly by regulating OAF production as well as directly by osteoclast activation. The interactions of OAF and prostaglandins at bone resorbing sites may be important in inflammatory and neoplastic diseases associated with bone destruction.

Prostaglandins are necessary for osteoclast-activating factor production by activated peripheral blood leukocytes.

The production of osteoclast-activating factor (OAF) by normal human peripheral blood leukocytes stimulated by phytohemagglutinin was inhibited by a series of structurally unrelated inhibitors of prostaglandin synthetase. Inhibition of OAF production by these agents was reversed by adding prostaglandins of the E series back to the leukocyte suspension. These results indicate that prostaglandin synthesis is necessary for OAF production.

Production of osteoclast-activating factor by normal human peripheral blood rosetting and nonrosetting lymphocytes.

This study has tested the ability of human mononuclear cells and the subpopulations of lymphocytes that rosette (E-RFC) or do not rosette (non-E-RFC) with sheep red blood cells to synthesize DNA and to produce a mediator with bone resorbing activity (osteoclast-activating factor, OAF) in response to stimulation with phytohemagglutinin (PHA). Mononuclear cells were stimulated by PHA both to synthesize DNA and to produce a factor that caused bone resorption. E-RFC enriched for T lymphocytes and depleted of macrophages synthesized considerable DNA in response to stimulation with PHA, but were unable to produce significant bone resorbing activity in tissue culture unless macrophages were re-added to the E-RFC. In contrast, mononuclear cells depleted of E-RFC (non-E-RFC enriched for B cells) did not synthesize DNA in response to stimulation with PHA, but did produce a mediator that caused significant bone resorption in tissue culture. In most of the experiments, unstimulated non-E-RFC produced as much OAF as the PHA-stimulated non-E-RFC. These results suggest that both activated T lymphocytes (E-RFC) and B lymphocytes (non-E-RFC) can produce OAF.

Macrophage-Lymphocyte Synergy in the Production of Osteoclast Activating Factor

Abstract Supernatants from cultures of activated normal human peripheral blood leukocytes contain a factor which stimulates osteoclastic bone resorption in vitro. The present study indicates that osteoclast activating factor (OAF) is produced by phytohemagglutinin-activated mononuclear cells within 6 hr of activation, and that peak production is associated with increased amino acid incorporation into protein but precedes increased thymidine incorporation into DNA. Granulocytes, platelets, and red cells were not necessary for the production of OAF, since mononuclear cells purified on Ficoll-Hypaque gradients and devoid of these elements produced as much OAF as unseparated leukocytes. Granulocyte extracts did not show bone-resorbing activity. The production of OAF by mononuclear cells was impaired by irradiation, suggesting that it is made by radiosensitive lymphocytes rather than radioresistant macrophages. However, OAF was not produced by lymphocytes purified on glass-bead columns although these cells could respond to phytohemagglutinin with increased thymidine and amino acid incorporation. Purified macrophages also failed to produce substantial bone-resorbing activity. However, when a small number of irradiated but viable macrophages (5 × 104 cells/ml) was added to glass bead-purified lymphocytes (2 × 106 cells/ml), OAF production was as great as with unseparated mononuclear cell populations. These results suggest that OAF is produced by lymphocytes, but that its production is dependent on macrophage-lymphocyte interaction. OAF is a unique bone-resorbing factor which may play an important role in bone lesions associated with chronic inflammation and neoplasia. The cellular mechanisms for its production participate in the pathogenesis of these disorders.