Endothelial cells: A novel key player in immunoregulation in acute graft-versus-host disease?

Graft-versus-host disease (GVHD) is a lethal complication of allogeneic hematopoietic stem cell transplantation where activated donor T cells attack the genetically disparate host cells. The main target organs of the T cells in GVHD are the skin, liver, and intestine. in order to explain why the lung, one of the barrier organs, is spared from the injury of effector T cells, we hypothesize that endothelial cells are essential for immune regulation in acute GVHD. The proposed mechanism including Th1 cells apoptosis induced by endothelial cells expressing Tim-3 ligand galectin-9, and differential expression levels of galectin-9 on endothelial cells in various organs. The elucidation of the detailed cellular and molecular mechanisms that involved may help to a better understanding of immunoregulation in acute GVHD. Furthermore, the hypothesis may offer improved insight into new therapeutic strategy to reduce the severity of GVHD. (C) 2009 Elsevier Ltd. All rights reserved.