1. Laboratory of Immunology, AIDS Research Center; National Institute of Health; Shinjuku-ku Tokyo 162 Japan
2. The Japanese Red Cross Central Blood Center; Japan Red Cross Hospital; Shibuya-ku Tokyo 150 Japan
3. Department of Medicine; Teikyo University Medical School; Itabashi-ku Tokyo 173 Japan
4. Department of Internal Medicine; Jikei University Medical School; Minato-ku Tokyo 105 Japan