1. Department of Medicine, Children's Hospital Boston, Dana Farber Cancer Institute, Boston, Massachusetts 02115.
2. Department of Pediatrics, Harvard Medical School, Dana Farber Cancer Institute, Boston, Massachusetts 02115.
3. Department of Biostatistics and Computational Biology, Dana Farber Cancer Institute, Boston, Massachusetts 02115.
4. Therion Biologics, Cambridge, Massachusetts 02142.
5. Duke University, Durham, North Carolina 27706.
6. New England Regional Primate Center, Harvard Medical School, Southborough, Massachusetts 01772.