Role of gut microbiota in graft-versus-host disease.

Our understanding of graft-versus-host disease (GVHD) has mostly focused on the role of adaptive immunity in mediating host-recipient genetic disparity in the proinflammatory milieu. These experimental models rarely address the unique biology of GVHD whereby it targets mainly epithelial compartments of the intestine, skin, and liver. Recent discoveries of the role of the microbiota in health and disease have reinvigorated questions about how the innate immunity contributes to the pathogenesis of GVHD and perhaps explains its tissue tropism. In this review, we discuss findings indicating the potential role of pattern-recognition receptors of the innate immune system in mediating GVHD and present evidence that shows how the microbiota interact with the host to shape health and disease. These findings support a reevaluation of our current clinical practice and encourage further studies of the potential critical role of the gut microbiota in hematopoietic stem cell transplant which may lead to novel preventive and therapeutic targets against GVHD.