Table 1.
Part of immune cells involved in bone metabolism.
| Cell type | Cytokine | Bone metabolism target | References |
|---|---|---|---|
| Th1 cell | IFN-γ, IL-2, TNF-α, and GM-CSF | Inhibit osteoclast formation (IFN-γ degrades TRAF6) | 36 |
| Th2 cell | IL-4, IL-5, IL-10, and IL-13 | Inhibit osteoclast formation (IL-4, IL-5, and IL-13). Maintain anabolic activity of osteoblasts (promote the synthesis of PTH). | 37,38 |
| Th9 cell | IL-9 | Promote osteoclastogenesis (synergistically induces differentiation of CD4 + T cells into Th17 cells with TGF-β). | 39 |
| Th17 cell | IL-17A, IL-17F, IL-21, and IL-22 | Promote osteoclastogenesis (IL-17 promotes effector cell expression of RANKL). Inhibit osteoblast formation (IL-17 inhibits BMP-2 induced osteoblast differentiation). Promote bone resorption (IL-22 promotes the absorption activity of osteoclasts). | 40, 41, 42 |
| Treg cell | CTLA- 4, IL-10 | Inhibit osteoclast formation (CTLA-4 inhibits the production of RANKL and M-CSF). Inhibit osteoclast formation (IL-10 selectively inhibits calcium signaling downstream of RANK by inhibiting TREM-2 transcription). | 43 |
| NKT cell | IL-15, TNF-α, and IFN-γ | Recruiting monocytes (Upregulation of chemokine receptor and adhesion molecule expression). Promote osteoclastogenesis (IL-15 and RANKL synergistically induce osteoclastogenesis). Bidirectional regulation of osteoclast differentiation (TNF-α, IFN-γ). | 44,45 |
| γδT cell | IL-6, IFN-γ | Activate γδT cells to affect the regulation of osteoclastogenesis (IL-6 produces a promoting effect. IFN-γ production inhibition). | 8 |
TRAF6: TNF receptor-associated factor 6, PTH: parathyroid hormone, RANKL: receptor activator of nuclear factor-κB ligand, CTLA- 4: CD80/cytotoxic T-lymphocyte associated protein 4, NKT: natural killer T.