Immunologic reconstitution following stem cell transplantation

The efficacy of bone marrow transplantation is contingent on not only the eradication of malignancy and restoration of hematopoiesis, but also successful reconstitution of the immune system. Opportunistic infections, despite resolution of neutropenia, continue to be the major cause of nonrelapse mortality following HLA-matched sibling transplants and are often the main cause of overall mortality following unrelated marrow transplantation. In two unrelated transplant series published within the past year fatal viral, fungal, and/or parasitic infections accounted for 16% and 34% of the mortality observed in children and adults, respectively, following unrelated bone marrow transplantation. Unfortunately, mortality secondary to infection has not changed significantly following unrelated bone marrow transplantation over the past 5 years. T- and B-cell deficits after transplantation have been well recognized. During the past year, not only have additional defects been elucidated, but two successful strategies to overcome them, namely adoptive immunotherapy to restore cytomegalovirus and Epstein-Barr virus cellular immunity, have been reported.