In vitro and animal models suggest that GVHD is mediated by naïve T cells. The aim of this study is to decrease the rate and severity of GVHD after selective depletion of naïve CD45RA+ T cells from allogeneic hematopoietic stem cell grafts in patients with CIDs with high risk of severe GVHD, and to preserve immunity against pathogens in a population with high vulnerability to infections.