Histopathology of Bronchial Asthma and the Effects of Treatment
Asthma is a complex condition with an imprecise definition. The airways in fatal asthma are occluded by tenacious plugs consisting of a mixture of exudate and mucus. There is fragility of airway surface epithelium and thickening of the subepithelial reticular layer (referred to as the epithelial “basement membrane” by light microscopy). Bronchial vessel dilatation, congestion and oedema, hypertrophy of bronchial smooth muscle and mucus-secreting submucosal glands together with an inflammatory cell infiltrate contribute to thickening of the airway wall. An inflammatory cell infiltrate, comprising lymphocytes and ‘activated’ (EG2+) eosinophils with release of granular content in the latter, are features of fatal asthma and also of relatively mild stable atopic, intrinsic and occupational forms of asthma. Whilst widespread mast cell degranulation (apparent by a reduction in their number) is found in fatal asthma, it is not a feature of mild stable disease as evidenced by studies of the numbers of tryptase positive mast cells and by morphometry of cells examined by electron microscopy. Release of cytokines, particularly IL-5, by lymphocytes, favour selective eosinophil adhesion to endothelium and their differentiation, survival and activation in the mucosa. Short term treatment of atopic asthmatics with inhaled corticosteroid reduces the numbers of mast cells, eosinophils and the extent of eosinophil degranulation. However, neither short-term nor long-term corticosteroid treatment reduces the thickening of reticular basement membrane.
KeywordsMast Cell Cystic Fibrosis Chronic Bronchitis Allergy Clin Immunol Vasoactive Intestinal Polypeptide
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- 1.American Thoracic Society. Standards for the diagnosis and care of patients with chronic obstructive pulmonary disease (COPD) and asthma. Am Rev Respir Dis 1987;136:225–244.Google Scholar
- 10.Laitenen LA, Heino M, Laitenen A, Kava T, Haahtela T. Damage of the airway epithelium and bronchial reactivity in patients with asthma. Am Rev Respir Dis 1985;131:599–606.Google Scholar
- 13.McCarter JH, Vazquez JJ. The bronchial basement membrane in asthma: immunohistochemical and ultrastructural observations. Arch Path 1966;82:328–335.Google Scholar
- 16.Reid L. Pathology of chronic bronchitis. Lancet 1954;i:275–279.Google Scholar
- 20.Azzawi M, Jeffery PK, Frew AJ, Johnston P, Kay AB. Activated eosinophils in bronchi obtained at post-mortem from asthma deaths. J Clin Exp Allergy 1989;19:118.Google Scholar
- 22.Beasley R, Roche W, Roberts JA, Holgate ST. Cellular events in the bronchi in mild asthma and after bronchial provocation. Am Rev Respir Dis 1987;139:806–817.Google Scholar
- 25.Jeffery PK, Godfrey RW, Adelroth E, Nelson F, Rogers A, Johansson S-A. Effects of treatment on airway inflammation and thickening of reticular collagen in asthma: a quantitative light and electron microscopic study and correlation with BAL. Am Rev Respir Dis, in press.Google Scholar
- 27.Bradley BL, Azzawi M, Jacobson M, Assoufi B, Collins JV, Irani A-MA, Schwartz LB, Durham SR, Jeffery PK, Kay AB. Eosinophils, T-lymphocytes, mast cells, neutrophils and macrophages in bronchial biopsies from atopic asthmatics: comparison with atopic non-asthma and relationship to bronchial hyperresponsiveness. J Allergy Clin Immunol 1991;88:Google Scholar
- 34.Djukanovic R, Wilson JW, Britten KM, Wilson SJ, Walls AF, Roche WR, Howarth PH, Holgate ST. Quantitation of mast cells and eosinophils in the bronchial mucosa of symptomatic atopic asthmatics and healthy control subjects using immunohistochemistry. Am Rev Respir Dis 1990;142:863–871.PubMedGoogle Scholar
- 36.Jeffery PK. Innervation of airway epithelium. In: Kay AB, ed. Asthma: clinical pharmacology and therapeutic progress. Blackwell, 1986;376–392.Google Scholar
- 40.Shipperbottom CA, Jeffery PK, Jones CJ. Preliminary studies on pulmonary innervation and alterations in cystic fibrosis. J Pathol 1987;Google Scholar
- 42.Sharma RK, Jeffery PK. Airway V.I.P. receptor number is reduced in cystic fibrosis but not asthma. Am Rev Respir Dis 1990;141:A726.Google Scholar