1. Bone Marrow Transplantation Unit, Hematology Branch, National Heart, Lung and Blood Institute, Bethesda, Maryland, U.S.A.,
2. Department of Transfusion Medicine, Warren Grant Magnuson Clinical Center, National Institutes of Health, Bethesda, Maryland, U.S.A.,
3. Department of Haematology, University of Crete School of Medicine, University Hospital of Heraklion, Crete, Greece