CD34 and graft versus host disease: We demonstrate that a short treatment of MPBCs with Fas ligand (FasL, CD95L) for 2 h using a closed automated cell processing system selectively induces apoptosis of specific donor T cells, B cells and antigen presenting cells, but, critically, not CD34+ hematopoietic stem cells and progenitors, all of which may contribute to an increased likelihood of graft survival and functionality and reduced GvHD.