1. Institute for Animal Experimentation, Faculty of Medicine, Hokkaido University, Kita 15, Nishi 7, Kita-ku, Sapporo, Hokkaido 060-8638, Japan
2. ICLAS Monitoring Center, Central Institute for Experimental Animals, 3-25-12 Tonomachi, Kawasaki, Kanagawa 210-0821, Japan
3. Laboratory of Animal Experimentation, Institute for Genetic Medicine, Hokkaido University, Kita 15, Nishi 7, Kita-ku, Sapporo, Hokkaido 060-0815, Japan
4. Department of Microbiology and Immunology, Faculty of Medicine, Hokkaido University, Kita 15, Nishi 7, Kita-ku, Sapporo, Hokkaido 060-8638, Japan