Antileukoprotease, its role in the human lung

The number of antileukoprotease-containing epithelial cells in the bronchioles of 27 surgically removed lungs shows a close positive correlation with inflammation of the small airways (bronchioles) and an inverse correlation with the number of undamaged alveolar walls surrounding the bronchioles. So, more antileukoprotease-producing cells are present when bronchioles and adjacent alveoli are more diseased. These results suggest that antileukoprotease-producing cells constitute part of the inflammatory response in and around bronchioles, serving to minimize local tissue destruction. The increased production of this potent elastase-inhibitor, however, seems insufficient to prevent tissue damage. We investigated in vitro whether antileukoprotease might be inactivated by stimulated polymorphonuclear leukocytes (PMN's). The antitryptic and antielastolytic capacities of antileukoprotease were rapidly destroyed by myeloperoxidase-derived oxidants from stimulated PMN's. It was observed that elastase, released by stimulated PMN's, retains full activity when cell stimulation was performed in the presence of a molar excess of antileukoprotease. These results indicate that inactivation of antileukoprotease by stimulated PMN's might be a factor which plays a role in elastase-mediated destruction of lung tissue.