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In summary, our data open a new perspective in the interaction between the immune system and the skeleton. The central concept of osteoimmunology that inflammatory T cell subsets such as activated Th1 cells and Th17 cells drive bone loss is now enriched by the concept that immune homeostasis is tightly linked to bone homeostasis. Thus, a key mechanism of immune regulation, the naturally occurring Foxp3+ regulatory T cells, transduces its favourable role in immune balance to skeletal homeostasis. This principle appears conceivable, because activation of the immune system and activation of bone resorption may go hand in hand. This may drive new concepts of a "bone protection system" and shape immunologic tools to maintain bone mass.

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Mario Zaiss finished his Ph.D. thesis at the Medical Clinic 3,Immunology and Rheumatology at the University ofErlangen-Nuremberg in 2009.

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