1. Department of Microbiology, University of Pennsylvania School of Medicine, Philadelphia, Pennsylvania.
2. Department of Pathology, University of Pennsylvania School of Medicine, Philadelphia, Pennsylvania.
3. Department of Pediatrics, Perelman School of Medicine, University of Pennsylvania School of Medicine, Philadelphia, Pennsylvania.
4. Department of Hematology, Children's Hospital of Philadelphia, Philadelphia, Pennsylvania.
5. New York Blood Center, New York, New York.
6. Departments of Pathology and Laboratory Medicine, Children's Hospital of Philadelphia, Philadelphia, Pennsylvania.