Fig. 7

Graphical abstract. a BMT pre-conditioning damages the thymus, which results in poor thymopoiesis and the generation of a restricted peripheral TCR repertoire. Consequently, the GVT effect is limited along with the appearance of GVHD induced by DLI. b Following IL-21 administration to transplanted mice, ST-HSCs and MPPs expand most likely leading to an increase in the pool of thymus-seeding progenitors. In parallel, IL-21 triggers the proliferation of thymic progenitors, which positively affects TECs resulting in accelerated recovery of a naïve T cell pool with a diversified TCR repertoire. The newly generated thymus-derived T cells promote GVT, while GVHD is controlled by homeostatic pressure on allogeneic T cells and via the action of IL-21-induced B10 cells