Akio Matsuda, Department of Allergy and Clinical Immunology, National Research Institute for Child Health and Development, 2-10-1 Okura, Setagaya-ku, 157-8535, Tokyo, Japan. Phone: +81-3-5494-7120 (ext. 4955); Fax: +81-3-5494-7173; E-mail: matsuda-a@ncchd.go.jp