1. Department of Pathology, Feinberg School of Medicine, Northwestern University, Chicago, IL 60208
2. Department of Pharmacology, Weill Medical College of Cornell University, New York, NY 10065
3. Laboratory of Immunochemistry, WPI Immunology Frontier Research Center and Department of Immunochemistry, Research Institute for Microbial Diseases, Osaka University, Osaka 565-0871, Japan