1. From the Chester Beatty Laboratories, Institute of Cancer Research, London, UK; the Department of Pathology and School of Public Health, Columbia University, New York, NY; the Clinical Sciences Department, London School of Hygiene and Tropical Medicine, University of London, London, UK; the Department of Pathology, Stanford University School of Medicine, Stanford, CA; and the Department of Pathology, Mount Sinai School of Medicine, New York, NY.