Cellular therapies for graft versus host disease: a tale of tissue repair and tolerance.
The success of allogeneic hematopoietic cell transplantation (HCT) depends heavily on the delicate balance between the activity of the donor immune system against malignant and non-malignant cells of the recipient. Abrogation of alloreactivity will lead to disease relapse, while untamed allo-immune responses will lead to lethal graft versus host disease (GvHD). A number of cell types have been identified that can be employed to suppress alloreactive immune cells and prevent lethal GvHD in mice. Of those, mesenchymal stromal cells (MSC) and to a lesser extent regulatory T cells (Treg) have demonstrated efficacy in humans. Ideally, cellular therapy for GvHD will not impact on alloreactive immune responses against tumor cells. The importance of tissue damage in the pathophysiology of GvHD rationalizes the development of cells that support tissue homeostasis and repair, such as innate lymphoid cells (ILC). We here discuss recent developments in the field of cellular therapy to prevent and treat acute and chronic GvHD, in the context of GvHD pathophysiology.