[1] Univ Tokyo, Inst Med Sci, Dept Pediat Hematol Oncol, Tokyo, Japan
[2] Univ Tokyo, Inst Med Sci, Dept Hematol Oncol, Tokyo, Japan
[3] Nippon Med Sch, Dept Pediat, Tokyo 113, Japan
[4] Hokkaido Univ, Sch Med, Dept Pediat, Sapporo, Hokkaido 060, Japan
[5] Kyoto Univ, Dept Pediat, Kyoto 606, Japan
[6] Cent Inst Expt Anim, Kawasaki, Kanagawa, Japan