Allogeneic hematopoietic stem cell transplantation (HSCT) remains the only treatment option for several severe hematological malignancies. The development of graft-versus-host disease (GVHD) is a common complication of the procedure and results when donor T cells become activated against recipient-specific antigens. The factors that drive the alloreactive T cell response are not completely understood. In this issue of the
Stromal cells directly activate Notch on allogeneic T cells.