1. Department of Internal Medicine, Washington University School of Medicine, St. Louis, MO 63110, USA.
2. Department of Immunology, Monsanto Company, St. Louis, MO 63198, USA.
3. Department of Epidemiology and Public Health, Yale University School of Medicine, New Haven, CT 06510, USA.
4. Howard Hughes Medical Institute, Washington University School of Medicine, St. Louis, MO 63110, USA.
5. Department of Molecular Biology and Pharmacology, Washington University School of Medicine, St. Louis, MO 63110, USA.