Author's Organization:Laboratory of Biomedical Science, College of Agriculture and Veterinary Medicine, Nihon Unviersity Laboratory of Biomedical Science, College of Agriculture and Veterinary Medicine, Nihon Unviersity Laboratory of Biomedical Science, College of Agriculture and Veterinary Medicine, Nihon Unviersity Laboratory of Biomedical Science, College of Agriculture and Veterinary Medicine, Nihon Unviersity Laboratory of Immune Cytology, National Institute of Animal Health