Figure 2.

The balance between effector T cells and Tregs in the distinct post-HSCT environment. After HSCT, donor-derived T cells are exposed to a variety of endogenous factors, including lymphopenia, alloantigens, danger signals, and cytokine storm, which affect the reconstitution of donor-derived immune cells. In addition, therapeutic interventions that have immunomodulating effects during the peri-transplant period also affect donor-derived T cell homeostasis. Unbalanced immune reconstitution may provide a basis for the pathogenesis of GVHD. In contrast, favorable Treg recovery in the post-transplant environment results in the induction of immune tolerance. GVHD, graft-versus-host disease; Treg, regulatory T cell; HSCT, hematopoietic stem cell transplantation; IL-2: interleukin 2, ICI, immune checkpoint inhibitor; PTCy, post-transplant cyclophosphamide.