Plasma exudation and oedema in asthma.

Gross pathology, histological and ultrastructural observations and analysis of sputum and lavage fluid indicate that plasma exudation from the bronchial microvasculature and the formation of tissue oedema are characteristic features of asthma. Appropriate mediators for the induction of plasma exudation are generated in the blood and airways of asthmatic patients and when administered experimentally will cause plasma leakage and oedema. Plasma exudate may not only contribute directly to the thickened bronchial walls and mucus plugs in the airways of asthmatics, but may also play a role in epithelial shedding, thickening of the basement membrane, hypertrophy of the smooth muscle, inducing mucus secretion and in thickening the secreted mucus. The beneficial effect of corticosteroids in asthma may be due to an anti-leakage action. Development of drugs with a broad spectrum of action against mediator release may have therapeutic advantage over specific receptor antagonist drugs.