Vitamin D deficiency, autoimmunity, and graft-versus-host-disease risk: Implication for preventive therapy.

The majority of patients after allogeneic stem cell transplantation (HSCT) are expected to have vitamin D deficiency early post HSCT due to poor nutritional status and limited sun exposure. The importance of vitamin D in the immune system has been well defined during the past several years, as vitamin D has demonstrated modulatory effects on the immune system through B and T-lymphocyte, macrophage, monocyte, and dendritic cell regulations, which are the effector cells involved in graft-versus-host-disease (GVHD) pathophysiology after HSCT. High-dose early replacement of vitamin D might attenuate autoimmune reactions and decrease severity of GVHD. In this article, we discuss the hypothetical link between early vitamin D deficiency and GVHD and its potential therapeutic role in GVHD and long-term bone loss after HSCT.