1. Department of Molecular Cell Biology, Sungkyunkwan University School of Medicine, Samsung Biomedical Research Institute, Suwon 440-746, Korea.
2. Division of Pulmonary and Critical Care Medicine, Department of Internal Medicine, College of Medicine Pochon CHA University, Seongnam 463-712, Korea.
3. Department of Laboratory Medicine College of Medicine, Seoul National University Seoul 110-744, Korea.
4. Division of Pulmonary and Critical Care Medicine, Department of Internal Medicine, Asan Medical Center, College of Medicine, University of Ulsan, Clinical Research Center for Chronic Obstructive Airway Diseases, Seoul 138-736, Korea.