Osteoimmunology: shared mechanisms and crosstalk between the immune and bone systems

Abstract

Osteoimmunology is an interdisciplinary field, that covers the shared mechanisms and interactions between bone cells and immune cells Receptor activator of nuclear factor-κB (NF-κB) ligand (RANKL) is an osteoclast-differentiation factor that links the activated immune system and bone loss. In addition, abnormal bone homeostasis has been observed in various mice deficient in immunomodulatory molecules. Osteoclast differentiation is dependent on the transcription factor nuclear factor of activated T cells, cytoplasmic 1 (NFATc1), which is induced and activated by RANKL and its co-stimulatory (immunoglobulin-like) receptors. Interleukin-17 (IL-17)-producing T helper cells (T_H17 cells) are the key T-cell subset that links T-cell activation and bone destruction in autoimmune arthritis. Bone cells are involved in the maintenance and mobilization of haematopoietic stem cells. Osteoimmunology is becoming increasingly important for understanding the pathogenesis of, and developing new therapeutic strategies for, diseases that affect both systems.