1. From the Laboratory of Cellular Physiology and Immunology, The Rockefeller University, New York, New York 10021
2. Department of Pediatrics, University of Minnesota Medical School, Minneapolis, Minnesota 55455
3. From the Laboratory of Immunology, The Rockefeller University, New York, New York 10021
4. From the Howard Hughes Medical Institute, The Rockefeller University, New York, New York 10021