Central Roles of OX40L–OX40 Interaction in the Induction and Progression of Human T Cell–Driven Acute Graft-versus-Host Disease

Graft-versus-host disease (GVHD) is one of the major obstacles for the success of allogeneic hematopoietic stem cell transplantation. In this article, we report that the interaction between OX40L and OX40 is of critical importance for both induction and progression of acute GVHD (aGVHD) driven by human T cells. Anti-human OX40L mAb (hOX40L) treatment could thus effectively reduce the disease severity in a xenogeneic-aGVHD model in both preventative and therapeutic modes. Mechanistically, blocking OX40L–OX40 interaction with an anti-hOX40L reduces infiltration of human T cells in target organs, including liver, gut, lung, and skin. It also decreases IL-21– and TNF-producing T cell responses while promoting regulatory T cell responses without compromising the cytolytic activity of CD8⁺ T cells. Single blockade of hOX40L was thus more effective than dual blockade of IL-21 and TNF in reducing the severity of aGVHD as well as mortality. Data from this study indicate that OX40L–OX40 interactions play a central role in the pathogenesis of aGVHD induced by human T cells. Therapeutic strategies that can efficiently interrupt OX40L–OX40 interaction in patients might have potential to provide patients with an improved clinical benefit.