ABSTRACT
The acid-stable, antiprotease activity of human secretory leukocyte protease inhibitor (SLPI) was first identified in seminal fluid (1) and later in the secretions of the nasal, bronchial, and cervical mucosa as well as those of the parotid gland (2). SLPI’s physiological role appears to be that of antiprotease defense for these tissues against the enzymes of extravascular neutrophils (3). The involvement of activated oxygen species and nonspecific proteolysis in the pathogenic destruction of tissues within the respiratory tract and elsewhere is widely accepted. The presence of large amounts of proteolytic enzymes in purulent bronchial secretions is an old observation, as is the presence of plasma proteins, including alpha 1antitrypsin (4,5). Leukocyte proteinases, like elastase, were identified as the major enzymes responsible for the proteolytic activity (5,6). In such respiratory pa thologies, increased proteolytic activity and/or decreased protease inhibitory ca pacity result in a characteristic protease-inhibitor imbalance. In many chronic respiratory diseases, this imbalance is largely attributable to increased number and activation of neutrophils.
