The History of the “deutsche Maus”, the Origin of the dd Mouse Group

An inbred strain of mice, DDD, was established at the Institute for Infectious Diseases (so-called Denken in Japanese; currently called Institute of Medical Science, The University of Tokyo: Jms) in 1962 (Table 1) . Many interesting characteristics including development of pregnancy-dependent mammary tumors, presence ofFv-2s, a Friend leukemia virus-susceptible gene, high incidence of hydronephrosis and low level of natural killer (NK) cell activity have been reported in this strain of mice. Two congenic strains, DDD-Fv-2rand DDD-Mtv-2+, have been produced. Inbreeding ofddmice maintained at Denken was commenced in 1957 and the resulting inbred strain was named DDD afterddatDenken (Table 1) . The ancestors ofddmice had come from Germany. The process of introduction to Japan and the history of these mice were surveyed in the literatures (Table 2), since the description concerning them had been confused. As a result, the following history was confirmed: the original colony of mice of an unknown size was introduced from the Hoechst Company, Frankfurt a. m. Main, Germany into the Kitasato Institute, Tokyo, Japan by Dr. Tsuneo Komatsu under the direction of Dr. Sahachiro Hata in autumn, 1928 (Table 3) . Dr. Hata and his colleagues bred these mice to use for medical researches and called them“deutsche Maus” (Table 2) . Their descendants (one male and one female) were shipped to the Health Institute of Manchuria Railway, Talien (currently called Dalian), China on demand of Dr. Koji Ando in 1934 (Table 3) . Two males and eight females from the Talien colony were shipped back to Dr. Saburo Kojima, the Institute for Infectious Diseases, Tokyo, Japan in 1943 (Table 3) . They had been maintained without crossing with another colony at the Institute, from which mice were distributed to many institutes throughout Japan between 1944 and 1960, and served as the starting nuclei of many inbred or outbred strains (Table 1) . The“deutsche Maus”was named dd mice after“deutscheMaus atDenken”in 1952 (Table 1) . Thus, the mouse strains connected withddmice usually have D, DD or dd at the head in their names.