Accumulation of intraepithelial mast cells with a unique protease phenotype in TH 2-high asthma

• Published in: Journal of allergy and clinical immunology 2010, Vol.125 (5), p.1046-1053.e8
• Main Authors: Dougherty, Ryan H., MD, Sidhu, Sukhvinder S., PhD, Raman, Kavita, PhD, Solon, Margaret, BA, Solberg, Owen D., PhD, Caughey, George H., MD, Woodruff, Prescott G., MD, MPH, Fahy, John V., MD, MSc
• Format: Article
• Language: English
• Subjects: Allergy and Immunology
• ISSN: 0091-6749
• DOI: 10.1016/j.jaci.2010.03.003

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 (“TH 2 high” and “TH 2 low” asthma) based on epithelial cell gene signatures for the activity of TH 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 TH 2-high asthma compared with that seen in subjects with TH 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 TH 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 TH 2-high asthmatic epithelium.