1. Department of Pathology and Immunology, Washington University School of Medicine, 660 South Euclid, Box 8118, Saint Louis, MO 63110, USA.
2. Program in Molecular Pathogenesis, Skirball Institute of Biomolecular Medicine, New York University, 540 First Avenue, New York, NY 10016, USA.
3. Genentech, Department of Immunology, 530 Forbes Boulevard, One DNA Way, South San Francisco, CA 94080, USA.