1. Department of Immunology, Graduate School of Pharmaceutical Sciences, Hokkaido University, Kita-12 Nishi-6, Kita-Ku, Sapporo 060-0812, Japan
2. Program in Cellular Neuroscience, Neurodegeneration & Repair, Yale University School of Medicine, New Haven, CT 06536, USA
3. Department of Hematology, International University of Health and Welfare, 4-3 Kouzunomori, Narita, Chiba 286-8686, Japan