1. Pulmonary and Critical Care Division, Department of Medicine, University of Oklahoma Health Sciences Center, Oklahoma City, Oklahoma;
2. The Lundberg-Kienlen Lung Biology and Toxicology Laboratory, Department of Physiological Sciences, Center for Veterinary Health Sciences, Oklahoma State University, Stillwater, Oklahoma;
3. Department of Biostatistics and Epidemiology, University of Oklahoma Health Sciences Center, Oklahoma City, Oklahoma;
4. Department of Microbiology and Immunology, University of Oklahoma Health Sciences Center, Oklahoma City, Oklahoma; and
5. Veterans Affairs Medical Center, Oklahoma City, Oklahoma