1. Department of Immunology, Weizmann Institute of Science, Rehovot 76100, Israel.
2. Francis Crick Institute, London NW1 1AT, UK.
3. Department of Veterinary Resources, Weizmann Institute of Science, Rehovot 76100, Israel.
4. Regeneron Pharmaceuticals, Inc., 777 Old Saw Mill River, Tarrytown, NY 10591, USA.