Epithelial antimicrobial peptides and proteins: their role in host defence and inflammation.

Various antimicrobial mechanisms act in concert to protect the lung from infection by forming an efficient host defence system. Most microbial challenges are counteracted by elements of the innate immune system and antimicrobial peptides and proteins have been identified as key components of innate immunity. Although phagocytes are an important cellular source of these so-called endogenous antibiotics, it is now recognized that the airway epithelium is also a major site of synthesis. Antimicrobial peptides and proteins kill a wide variety of micro-organisms. Their importance is illustrated by the observation that in cystic fibrosis changes in the airway surface fluid may result in a dysfunction of these components. Recent studies have revealed other functions of these molecules showing they may link innate and adaptive immunity and appear to be involved in the regulation of inflammation and tissue repair.