The immune system and skeletal system are both dependent on each other. The skeletal system gives our body a basic framework and provides protection and structure. Bones are integral to our skeletal system and are also home to marrow, that produces lymphocytes (or white blood cells) which are essential components of our immune system.
It has been found that the skeletal system and immune system share signaling molecules, regulatory molecules (e.g., cytokines), membrane receptors and transcription factors. Such sharing also means that these systems are dependent on each other and deficient performance of one can affect the other. An example is rheumatoid arthritis, a disease that results in bone destruction and is a consequence of over-activation of the immune system. Animal models have also shown that lack of immunomodulatory molecules results in development of unexpected skeletal phenotypes.
Osteoimmunology is an emerging medical specialization that studies the interrelationship between the immune and skeletal systems.