Tight relationships between B lymphocytes and the skeletal system

• Deficiency in osteoblasts or osteocytes results in impaired B cell function.
• Perturbation of B lymphopoiesis has been linked to changes in bone mass.
• B cell derived osteoprotegerin is important for maintenance of the bone.
• B cell depletion therapy in rheumatoid arthritis reduces joint destruction.

Mounting evidence indicates that the immune system and the skeletal system share several regulatory nodes. B lymphocytes, which play key roles in immune homeostasis, are uniquely endowed with osteointeractive properties. From their early development to the plasma cell stage, they are in close proximity with the skeletal system and produce factors important for bone maintenance. Not surprisingly, perturbation of B lymphopoiesis affects bone mass. Reciprocally, inactivation of bone cell functions results in B cell development blocks. This new understanding is refining our insights into the pathogenesis of several diseases such as periodontitis and rheumatoid arthritis.