1Department of Pathology, Institute for Medical Immunology, Kumamoto University Medical School, 2-2-1 Honjo, Kumamoto, 860, Japan
2Department of Obstetrics and Gynecology, Kumamoto University Medical School, 2-2-1 Honjo, Kumamoto, 860, Japan
3Biomaterial Research Institute Co. Ltd, Yokohama, Kanagawa, 244, Japan
4Jackson Laboratory, Bar Harbor, Maine, 04609, USA