Objective:To explore the role of γδ T cells in the transdifferentiation of immature dendritic cells(imDC) into osteoclasts(OC). Methods:(1) Peripheral blood mononuclear cells(PBMNC) were cultured with zoledronate(Zol) and recombinant human interleukin-2(IL-2),and PBMNC from healthy volunteers were cultured with granulocyte macrophage colony-stimulating factor (GM-CSF) and recombinant human interleukin-4(IL-4) to differentiate into imDC,which were then cultured with receptor activator nuclear factor к B ligand(RANKL) and macrophage colony-stimulating factor(M-CSF) to differentiate into OC. The purity of γδ T cells,and phenotype changing of OC transdifferentiated from imDC were investigated by flow cytometry. (2) Co-culture system was es-tablished using millicell inserts.γδT cells isolated with immune magnetic bead were placed in the upper compartment and imDC in the lower compartment in the ratio of 10∶1. To explore the role of γδ T cells during differentiation of imDC into OC,tartrate resistant acid phosphatase( TRAP) staining and bone resorption observation staining were used. Tumor necrosis factor-alpha( TNF-α) of supernatant liquid from different cultures was measured using ELISA(Enzyme linked immunosorbent assay) kit. Results:(1) γδT cells can be ex-panded from PBMNC of MM patients, and the production capacity was similar to that of healthy volunteers ( 68. 87%± 20. 94% vs 69. 33%±16. 84%,P>0. 05 ) . ( 2 ) OC could be transdifferentiated from imDC when cultured with RANKL and M-CSF. ( 3 ) The number of TRAP+ multinuclear cell and the absorption area of dentine were significantly lower in the group of imDC indirectly co-cultured with γδ T cells than in the group of control imDC(5.67±0.58 vs 28.33±2.08,4.97%±4.3% vs 28.47%±12.8%, respectively). (4) Under the circumstance of γδ T cell-imDC indirect coculture,TNF-α got significantly higher. Conclusion: γδ T cells might inhibit the transdifferentiation of imDC into OC.γδ T cells-based immunotherapy is expected to be a new treatment for myeloma bone disease.