1. Department of Developmental Immunology, Chiba University School of Medicine, Graduate School of Medicine, Chiba University, Chiba 260-8670, Japan
2. Department of Pathology and Laboratory Medicine, University of Pennsylvania School of Medicine, Philadelphia, Pennsylvania 19104-6082
3. Program in Molecular Immunology, Institute of Molecular Medicine and Genetics, Medical College of Georgia, Augusta, Georgia 30912-2600
4. Department of Molecular Immunology, Graduate School of Medicine, Chiba University, Chiba 260-8670, Japan
5. Medicinal Biology Research Laboratories, Fujisawa Pharmaceutical Company, Limited, Osaka 532, Japan
6. Department of Experimental Surgery and Bioengineering, National Children's Medical Research Center, Tokyo 154, Japan