Alveolar macrophages lavaged from human lungs contain protease activity at an optimum pH of 3.0 and possibly a lesser peak of activity at pH 5.5. Protease activity measured at pH 4.1 is inhibited by purified alpha-1-antitrypsin. Fluorescent antibody studies of human alveolar macrophages showed that alpha-1-antitrypsin is present in normal alveolar macrophages. In addition, macrophages from a pa...
