1. Department of Molecular Genetics, Institute for Liver Research, Kansai Medical University
2. Department of Host Defense, Research Institute for Microbial Diseases, Osaka University, Suita, Osaka 565-0871, Japan
3. Laboratory for Lymphocyte Differentiation, RIKEN Research Center for Allergy and Immunology, 10-15 Fumizono-cho, Moriguchi, Osaka 570-8506, Japan
4. Division of Cell Biology, Institute of Life Science, Kurume University, Kurume, Fukuoka 839-0861, Japan