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OBJECTIVE: To investigate whether Treg cells can suppress osteoclast differentiation, and to define a new potential link between the immune system and the skeleton. METHODS: Regulatory CD4+,CD25+,Foxp3+ T cells were isolated and purified from the spleen and cocultured with CD11b+ osteoclast precursor cells isolated from bone marrow. Osteoclastogenesis and bone erosion were assessed by tartrate-resistant acid phosphatase staining and pit resorption assay, respectively. In addition, Transwell experiments and cytokine-blocking experiments were performed to define the mechanisms of interaction between Treg cells and osteoclasts. RESULTS: CD4+,CD25+,Foxp3+ T cells, but not CD4+,CD25- T cells, dose dependently inhibited macrophage colony-stimulating factor- and RANKL-dependent osteoclast formation. Pit formation was inhibited by up to 80% when Treg cells were added. The blockade of osteoclast formation was not based on the alteration of RANKL/osteoprotegerin balance but was essentially dependent on direct cell-cell contact via CTLA-4. Treg cell-mediated expression of transforming growth factor beta, interleukin-4 (IL-4), and IL-10 contributed but was not essential to the inhibitory effect on osteoclastogenesis. CONCLUSION: These data show that CD4+,CD25+,Foxp3+ Treg cells suppress osteoclast formation, provide a new link between the immune system and bone, and extend our knowledge on regulation of bone homeostasis by the immune system.

Original publication




Journal article


Arthritis Rheum

Publication Date





4104 - 4112


Animals, Antigens, CD, Antigens, Differentiation, Bone and Bones, CD11 Antigens, CTLA-4 Antigen, Cell Communication, Cell Differentiation, Cells, Cultured, Female, Forkhead Transcription Factors, Immune System, Interleukin-2 Receptor alpha Subunit, Macrophage Colony-Stimulating Factor, Mice, Mice, Inbred C57BL, Osteoclasts, RANK Ligand, T-Lymphocytes, Regulatory