1. Department of Hematology, Kumamoto University of Medicine, Kumamoto, Japan;
2. Medicine and Biosystemic Science, Kyushu University Graduate School of Medical Sciences, Fukuoka, Japan;
3. Department of Cell Pathology, Kumamoto University of Medicine, Kumamoto, Japan;
4. Division of Hematopoiesis, Center for AIDS Research, Kumamoto University, Kumamoto, Japan; and
5. Graduate School of Frontier Sciences, University of Tokyo, Tokyo, Japan