1. From the Department of Immunology, Schering-Plough Research Institute, Kenilworth, New Jersey 07033
2. From the Department of Drug Safety and Metabolism, Schering-Plough Research Institute, Kenilworth, New Jersey 07033
3. Department of Immunology, DNAX Research Institute, Palo Alto, California 94304
4. Department of Pathology, University of Michigan Medical School, Ann Arbor, Michigan 48109