Patients undergoing diagnostic bronchoscopy at the NIH Clinical Center may participate in this study. Patients will undergo bronchoscopy and bronchoalveolar lavage as scheduled for their medical care. For this procedure, the patient's mouth and throat are numbed with lidocaine; a sedative may be given for comfort. A thin flexible tube called a bronchoscope is advanced through the nose or mouth into the lung airways to examine the airways carefully. Saline (salt water) is then injected through the bronchoscope into the air passage, acting as a rinse. A sample of fluid is then withdrawn for microscopic examination. Researchers in the current study will use some of the fluid obtained from the lavage to examine for protein content.