Volunteers, who may be Veterans or non-Veterans, will be screened by a series of questionnaires, chest X-ray, spirometry, EKG, blood work, and a complete history and physician examination by a study physician. Those who qualify for the study and agree via informed consent, will undergo a fiberoptic bronchoscopy on a separate day for the initial visit. Bronchoscopy is a procedure in which a flexible video instrument is passed via the nose or mouth, through the vocal cords and into the lungs. During the procedure, portions of the lungs will be washed ("lavaged") with a salt water solution, to collect the alveolar macrophages. This procedure involves conscious sedation, so that a driver is required on the day of the bronchoscopy. The entire procedure, including placement of an intravenous line to administer medications, local anesthetics, the bronchoscopy itself, and the recovery period, takes about 2.5-3 hours. The cells collected by bronchoscopy will be studied in the research laboratory, and used entirely in that procedure.