1. Department of Internal Medicine, Seoul National University College of Medicine, Seoul 110-799, Korea.
2. Institute of Allergy and Clinical Immunology, Seoul National University Medical Research Center, Seoul 110-799, Korea.
3. Division of Allergy and Clinical Immunology, Department of Medicine, Faculty of Medicine, Allergy and Clinical Immunology Research Group, Chulalongkorn University, Bangkok 10330, Thailand.
4. Department of Internal Medicine, Seoul National University Bundang Hospital, Seongnam 463-707, Korea.
5. Department of Internal Medicine, Kyungpook National University School of Medicine, Daegu 800-842, Korea.