ABSTRACT
The function of antiproteases is to inhibit the activity of cognate proteases thereby preventing potentially damaging degradation of host tissue. In the context of the respiratory tract, the primary antiproteases of interest are alpha-1-antitrypsin (AAT), secretory leukoprotease inhibitor (SLPI), elafin, tissue inhibitors of metalloproteases (TIMPs), and cystatins. The primary protease targets of AAT, SLPI, and elafin are the serine proteases, neutrophil elastase (NE), proteinase 3, and cathepsin G, which are released by activated neutrophils. Tissue inhibitors of metalloproteases inhibit the activity of matrix metalloproteases (MMPs) that are released from activated neutrophils and macrophages, whereas cystatins inhibit the activity of elastolytic cathepsins that are released from macrophages, fibroblasts, and epithelial cells. Despite the emphasis on protease inhibitory function, it has become apparent in recent years that antiproteases possess other biological functions including antibacterial, anti-inflammatory, and immunomodulatory properties. In the course of this chapter, we will outline the biological function of each of the antiproteases mentioned earlier and discuss how antiprotease activity may be compromised in the setting of lung disease.
