[1] Royal Melbourne Hosp, Walter & Eliza Hall Inst Med Res, Parkville, Vic 3050, Australia
[2] Univ Tsukuba, Sch Med, Dept Surg, Ibaraki, Osaka 305, Japan
[3] Juntendo Univ, Sch Med, Dept Immunol, Bunkyo Ku, Tokyo 113, Japan
[4] Japan Sci & Technol Corp, JST, CREST, Chiyoda Ku, Tokyo 101, Japan