1. Division of Hematologic Malignancies, Dana-Farber Cancer Institute, and Department of Medicine, Harvard Medical School, Boston, MA 02115.
2. Immunology Research Division, Department of Pathology, Brigham and Women's Hospital and Harvard Medical School, Boston, MA 02115.
3. Experimental Immunology Branch, National Cancer Institute and National Institute on Aging, National Institutes of Health, Bethesda, MD 20892.
4. Division of Lymphocyte Biology, Dana- Farber Cancer Institute, and Department of Pathology, Harvard Medical School, Boston, MA 02115.
5. Repligen Corporation, Cambridge, MA 02139.