1. Institute for Biomedical Research, Teijin Ltd., 4-3-2 Asahigaoka, Hino 191, Japan, Department of Pathobiology, Nihon University School of Veterinary Medicine, 1866 Kameino, Fujisawa 252, Japan
2. Department of Pathobiology, Nihon University School of Veterinary Medicine, 1866 Kameino, Fujisawa 252, Japan
3. Institute for Biomedical Research, Teijin Ltd., 4-3-2 Asahigaoka, Hino 191, Japan