Accumulation of intraepithelial mast cells with a unique protease phenotype in T(H)2-high asthma
Ryan H Dougherty, Sukhvinder S Sidhu, Kavita Raman, Margaret Solon, Owen D Solberg, George H Caughey, Prescott G Woodruff, John V Fahy, Ryan H Dougherty, Sukhvinder S Sidhu, Kavita Raman, Margaret Solon, Owen D Solberg, George H Caughey, Prescott G Woodruff, John V Fahy
Abstract
Background: Previously, we found that mast cell tryptases and carboxypeptidase A3 (CPA3) are differentially expressed in the airway epithelium in asthmatic subjects. We also found that asthmatic subjects can be divided into 2 subgroups ("T(H)2 high" and "T(H)2 low" asthma) based on epithelial cell gene signatures for the activity of T(H)2 cytokines.
Objectives: We sought to characterize intraepithelial mast cells (IEMCs) in asthma.
Methods: We performed gene expression profiling in epithelial brushings and stereology-based quantification of mast cell numbers in endobronchial biopsy specimens from healthy control and asthmatic subjects before and after treatment with inhaled corticosteroids (ICSs). We also performed gene expression and protein quantification studies in cultured airway epithelial cells and mast cells.
Results: By means of unsupervised clustering, mast cell gene expression in the airway epithelium related closely to the expression of IL-13 signature genes. The levels of expression of mast cell genes correlate positively with lung function improvements with ICSs. IEMC density was 2-fold higher than normal in subjects with T(H)2-high asthma compared with that seen in subjects with T(H)2-low asthma or healthy control subjects (P = .015 for both comparisons), and these cells were characterized by expression of tryptases and CPA3 but not chymase. IL-13 induced expression of stem cell factor in cultured airway epithelial cells, and mast cells exposed to conditioned media from IL-13-activated epithelial cells showed downregulation of chymase but no change in tryptase or CPA3 expression.
Conclusion: IEMC numbers are increased in subjects with T(H)2-high asthma, have an unusual protease phenotype (tryptase and CPA3 high and chymase low), and predict responsiveness to ICSs. IL-13-stimulated production of stem cell factor by epithelial cells potentially explains mast cell accumulation in T(H)2-high asthmatic epithelium.
Conflict of interest statement
Disclosure of potential conflict of interest: G. H. Caughey receives research support from the National Institutes of Health (NIH)/National Heart, Lung, and Blood Institute. P. G. Woodruff receives research support from Genentech. J. V. Fahy has consultant arrangements with Amira, Cytokinetics, Abbott, and GlaxoSmithKline and receives research support from Genentech and the NIH. The rest of the authors have declared that they have no conflict of interest.
Copyright 2010 American Academy of Allergy, Asthma & Immunology. Published by Mosby, Inc. All rights reserved.
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Source: PubMed