1. H.-W. Mittrücker, A. Grossman, T. M. Kündig, J. Potter, A. Shahinian, A. Wakeham, P. S. Ohashi, T. W. Mak, Departments of Immunology and Medical Biophysics, University of Toronto, and the Amgen Institute, 610 University Avenue, Toronto, Ontario, M5G 2C1, Canada.
2. T. Matsuyama, Department of Oncology, Faculty of Medicine, Nagasaki University, Nagaskai, Japan.
3. B. Patterson, Department of Oncologic Pathology, Ontario Cancer Institute, 610 University Avenue, Toronto, Ontario, M5G 2C1, Canada.