AUTHOR=Neidemire-Colley Lotus , Robert Jérémy , Ackaoui Antoine , Dorrance Adrienne M. , Guimond Martin , Ranganathan Parvathi TITLE=Role of endothelial cells in graft-versus-host disease JOURNAL=Frontiers in Immunology VOLUME=Volume 13 - 2022 YEAR=2022 URL=https://www.frontiersin.org/journals/immunology/articles/10.3389/fimmu.2022.1033490 DOI=10.3389/fimmu.2022.1033490 ISSN=1664-3224 ABSTRACT=Allogeneic hematopoietic transplantation (allo-HCT) is the only curative treatment for patients with refractory or high-risk hematologic malignancies who do not respond to conventional chemotherapy. Acute graft-versus-host disease (GVHD) mediated by alloreactive T cells in the donor graft is a frequently fatal complication and the leading cause of non-relapse mortality (NRM) in patients post allo-HCT. The pathogenesis of acute GVHD involves recognition of minor and/or major HLA mismatched host antigens by donor T cells followed by expansion, migration and finally end-organ damage due to combination of inflammatory cytokine secretion and direct cytotoxic effects. The endothelium is a thin layer of endothelial cells (EC) that line the innermost portion of the blood vessels and a key regulator in vascular homeostasis and inflammatory responses. Endothelial cell activation and dysfunction plays a role in multiple post-transplant complications including but not limited to veno-occlusive disease (VOD), transplant associated thrombotic microangiopathy (TA-TMA), and idiopathic pneumonia syndrome, reviewed elsewhere. In this mini review, we summarize the biology of endothelial cells, factors regulating EC activation and the role of ECs in inflammation and GVHD pathogenesis.