With current techniques, the risk of graft rejection is 1–3%, and the risk of severe, life-threatening acute GVHD is ~15% following transplantation between HLA-identical siblings. The incidence of graft rejection and GVHD increases progressively with the use of family member donors mismatched for one, two, or three antigens. While survival following a one-antigen mismatched transplant is not markedly altered, survival following two- or three-antigen mismatched transplants is significantly reduced, and such transplants should be performed only as part of clinical trials. Since the formation of the National Marrow Donor Program, it has become possible to identify HLA-matched unrelated donors for. | Chapter 108. Hematopoietic Cell Transplantation Part 2 With current techniques the risk of graft rejection is 1-3 and the risk of severe life-threatening acute GVHD is 15 following transplantation between HLA-identical siblings. The incidence of graft rejection and GVHD increases progressively with the use of family member donors mismatched for one two or three antigens. While survival following a one-antigen mismatched transplant is not markedly altered survival following two- or three-antigen mismatched transplants is significantly reduced and such transplants should be performed only as part of clinical trials. Since the formation of the National Marrow Donor Program it has become possible to identify HLA-matched unrelated donors for many patients. The genes encoding HLA antigens are highly polymorphic and thus the odds of any two unrelated individuals being HLA-identical are extremely low somewhat less than 1 in 10 000. However by identifying and typing 7 million volunteer donors HLA-matched donors can now be found for 50 of patients for whom a search is initiated. It takes on average 3-4 months to complete a search and schedule and initiate an unrelated donor transplant. Results so far suggest that GVHD is somewhat increased and survival somewhat poorer with such donors than with HLA-matched siblings. Autologous transplantation involves the removal and storage of the patient s own stem cells with subsequent reinfusion after the patient receives highdose myeloablative therapy. Unlike allogeneic transplantation there is no risk of GVHD or graft rejection with autologous transplantation. On the other hand autologous transplantation lacks a graft-versus-tumor GVT effect and the autologous stem cell product can be contaminated with tumor cells that could lead to relapse. A variety of techniques have been developed to purge autologous products of tumor cells. Some use antibodies directed at tumor-associated antigens plus complement antibodies linked to toxins or .
