Neutrophil elastase (NE), a powerful proteolytic enzyme found within the primary cytoplasmic granules of polymorphonuclear leukocytes (PMN), is capable of degrading almost any component of the extracellular pulmonary matrix and forms part of the cells’ armoury against invading microbes (Crystal, 1996; Haslett, Savill and Meagher, 1989). It is essential during inflammation for diapedesis and migration to extravascular compartments (Henson and Johnson, 1987), oxygen independent bactericidal activity and the remodelling of damaged tissues (Ganz, Metcalf, Gallin and Lehrer, 1987) and is crucial for health as an absence results in increased susceptibility to pyogenic infections which, if untreated, are eventually fatal. Mature PMN contain a finite amount of NE (Campbell, Silverman and Campbell, 1989) which can only be synthesized during development within the bone marrow, especially the pro–myelocyte stage (Fouret, duBois, Bernaudin, Takahashi, Ferrans and Crystal, 1989).
PMN are often the first white blood cells to be attracted to an inflamed and/or infected area within the body and can persist there due to their role in remodelling damaged tissue.