1. Department of Epidemiology, University of North Carolina at Chapel Hill, Chapel Hill, North Carolina, USA
2. Biological Sciences Division, Pacific Northwest National Laboratories, Richland, Washington, USA
3. Marsico Lung Institute Tissue Procurement and Cell Culture Core, University of North Carolina at Chapel Hill, Chapel Hill, North Carolina, USA
4. Department of Cell Biology and Physiology, University of North Carolina at Chapel Hill, Chapel Hill, North Carolina, USA