Osteoimmunology as an intrinsic part of immunology

Osteoimmunology has emerged as a field linking immunology and bone biology, but it has yet to be recognized as belonging to mainstream immunology. However, the extent of the research fields immunology actually covers has been enormously widened, and it is now ready to include such an interdisciplinary subject. One of the most obvious examples of an interaction between the immune and bone systems is the pathogenesis of rheumatoid arthritis, where bone resorption is increased by the autoimmune response. Moreover, the regulation of the immune system by bone cells has been clearly demonstrated by the finding that osteoprogenitor cells contribute to hematopoietic stem cell maintenance as well as the suppression of hematopoietic malignancy. Thus, the bidirectional dialogue has been established and inevitably will lead to the union of bone and immunity. Here, I summarize the history and concept of osteoimmunology, providing a perspective on the future of immunology.