1. Department of Transfusion Medicine, Warren Grant Magnuson Clinical Center;
2. Molecular Hematology Section, National Institute of Diabetes, Digestive and Kidney Diseases;
3. Hematology Branch, National Heart, Lung and Blood Institute;
4. Experimental Transplantation and Immunology Branch, National Cancer Institute;
5. Laboratory of Host Defenses, National Institute of Allergy, Immunology and Infectious Diseases; and
6. Biostatistics and Clinical Epidemiology Service, Clinical Center; National Institutes of Health, Bethesda, MD