[Aberrant bone remodeling during sepsis.]

Sepsis is a systemic inflammatory response syndrome that occurs upon severe bacterial infection. Although the development of early treatment for sepsis improves the survival rate of sepsis patients, in the subacute phase, certain patients suffer from secondary infection due to immunosuppression. It has been reported that one of the causes of the immunocompromised state during sepsis is lymphopenia. However, the underlying mechanisms are not well understood. We found that acute inflammation induced the immunodeficiency caused by the reduction of the numbers of peripheral lymphocytes and common lymphoid progenitors(CLPs)in the bone marrow, which was associated with a dramatic decrease in the osteoblast number. Osteoblast-specific deletion of IL-7 provided evidence for the role of osteoblasts in the regulation of lymphopoiesis in systemic inflammation. An acute loss of osteoblasts in sepsis induced the disturbance of lymphocyte homeostasis, resulting in immunodeficiency.