1. Department of Polymer Chemistry, Graduate School of Engineering, Kyoto University, Katsura, Nishikyo-ku, Kyoto 615-8510, Japan
2. WPI Immunology Frontier Research Center, Osaka University, Suita, Osaka 565-0871, Japan
3. Biomedical MR Science Center, Shiga University of Medical Science, Seta Tsukinowa-cho, Otsu 520-2192, Japan