Neutrophiles et asthme aigu grave

Abstract

Severe asthma attacks can be triggered by number of factors, including allergens, irritants, viruses responsible for severe bronchoconstriction, and bronchial inflammation involving activated eosinophils and neutrophils. The key role of eosinophils in asthma, and in attacks of asthma, is well known, whereas the role of neutrophils has not been studied extensively. Neutrophils are present in the sputum and bronchial lavage fluid of children and adults during acute asthma attacks and during status asthmaticus. In these situations, viruses, but also allergens and endotoxin are able to recruit neutrophils via IL-8 production by activated epithelial cells or macrophages. The role of corticosteroids also needs to be considered: it decreases eosinophil counts, but activates neutrophil progenitors and inhibits neutrophil apoptosis. In severe asthma attacks, various mediators secreted by neutrophils can enhance bronchial inflammation, hyperresponsiveness, the “plugs” phenomenon and bronchial permeability. The contribution of metalloproteinase-9, (secreted mainly by neutrophils) in bronchial inflammation has been recently demonstrated in patients with severe asthma attacks and in those with status asthmaticus.