One reason that people with COPD experience shortness of breath and cough is because the lung airways are partly damaged and obstructed. In healthy people, oxygen is breathed in and then passes easily into the bloodstream through bunches of small air sacs that fill the lungs. In people with COPD, these air sacs are damaged, making it difficult for oxygen to pass into the bloodstream. However, even in people with severe COPD, the air sacs in some areas of the lungs continue to work, even though neighboring air sacs are damaged. It is possible that an overactive immune response may cause the air sac damage and that some people with COPD are more prone than others to such immune system abnormalities. By examining the differences in lung tissue in people with and without COPD who are undergoing a lung transplant, this study will investigate why some people's immune systems cause lung damage and others do not and how and why some air sacs are damaged while other nearby air sacs are not. Study researchers will also examine whether genetic factors play a role in the development and severity of COPD.