The T-lymphocytes present in the graft, HLA compatibility, and the cytokine environment at the time of transplantation play a major role in alloreactivity. Increased knowledge of the on-going immunological interactions as well as the development of cellular therapy are required to permit further expansion of post-transplantation alloreactivity as an important immunotherapy tool. By allowing successful GvHD prevention and various post-transplantation immunological interventions, T-cell depletion of the graft can be the starting point for a multistage "progressive" procedure transplantation process adapted to recipient disease, HLA compatibility, desired anti-tumour effects and observed alloreactivity.