Release of elastase from purified human lung mast cells and basophils - Identification as a Hageman factor cleaving enzyme

Elastase, a serine protease, is capable of inducing severe lung destruction in experimental animal models. We now report that this proteinase exists preformed in neutrophil-free sonicates of purified human lung mast cells (>98% purity) and in circulating peripheral blood basophils (>97% purity). The elastase levels in both cell types (41-174 ng/10⁶ cells) represents approximately 3-20% of those found in human neutrophils; both cell types released their elastase following anti-IgE and ionophore A23187 challenge. The apparent molecular size of the mast cell enzyme on Sephadex G-100 gel filtration, as well as its inhibition profile, was identical to that of purified human neutrophil elastase. This mast cell elastase is identical to our previously reported mast cell-derived Hageman factor cleaving activity. Mast cell-, basophil-, and neutrophil-derived elastases cleave Hageman factor into fragments of 52,000 and 28.000 Da; cleavage by all three enzymes is inhibited by preincubation with polyclonal antibodies directed against human neutrophil elastase.