1. Department of Immunology, Institute of Basic Medical Sciences, University of Tsukuba, and CREST (JST), Tsukuba, Ibaraki 305-8575, Japan
2. Department of Surgery, Institute of Clinical Medicine, University of Tsukuba, Tsukuba, Ibaraki 305-8575, Japan
3. Institute of Basic Medical Sciences and Center for Tsukuba Advanced Research Alliance, Institute of Basic Medical Sciences
4. Department of Anatomy and Embryology, Institute of Basic Medical Sciences
5. Laboratory of Stem Cell Therapy, Center for Experimental Medicine, The Institute of Medical Science, University of Tokyo, Tokyo 108-8639, Japan
6. College of Medical Technology and Nursing, Institute of Clinical Medicine, University of Tsukuba, Tsukuba, Ibaraki 305-8575, Japan