CD34 and graft versus host disease: Although ex vivo TCD in haploSCT is most commonly achieved by positive selection of CD34+ cells, negative selection of lymphocyte subsets through CD3/CD19 or TCRαβ retains other donor immune cells, i.e. natural killer (NK) cells, that may decrease the incidence of GVHD and exert a graft-versus-leukemia effect [10].