1. Integrated Program in Cell, Molecular and Biophysical Studies, the
2. DNAX Research Institute of Molecular and Cellular Biology, Palo Alto, California 94304
3. Department of Medicine, College of Physicians and Surgeons, Columbia University, New York, New York 10032
4. Department of Pathology, College of Physicians and Surgeons, Columbia University, New York, New York 10032
5. Department of Microbiology, College of Physicians and Surgeons, Columbia University, New York, New York 10032