1. Y. Wei, D. I. Simon, H. A. Chapman, Department of Medicine, Brigham and Women's Hospital and Harvard Medical School, Boston, MA 02115, USA.
2. M. Lukashev, Department of Stomatology, University of California, San Francisco, CA 94143, USA.
3. S. C. Bodary, Genentech, South San Francisco, CA 94080, USA.
4. S. Rosenberg and M. V. Doyle, Chiron Corporation, Emeryville, CA 94608, USA.