title: Accumulation of intraepithelial mast cells with a unique protease phenotype in T(H)2-high asthma.
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.
  
  
  OBJECTIVE
  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.
  
  
  CONCLUSIONS
  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.
authors.affiliation: Division of Pulmonary and Critical Care Medicine, University of California, San Francisco, CA, USA.
authors.forename: Ryan H
authors.initials: RH
authors.lastname: Dougherty
authors.forename: Sukhvinder S
authors.initials: SS
authors.lastname: Sidhu
authors.forename: Kavita
authors.initials: K
authors.lastname: Raman
authors.forename: Margaret
authors.initials: M
authors.lastname: Solon
authors.forename: Owen D
authors.initials: OD
authors.lastname: Solberg
authors.forename: George H
authors.initials: GH
authors.lastname: Caughey
authors.forename: Prescott G
authors.initials: PG
authors.lastname: Woodruff
authors.forename: John V
authors.initials: JV
authors.lastname: Fahy
mesh_terms: D000328:Adult; D001249:Asthma / Q000276:immunology / Q000503:physiopathology; D043422:Carboxypeptidases A / Q000235:genetics / Q000378:metabolism; D002478:Cells, Cultured; D053818:Chymases / Q000235:genetics / Q000378:metabolism; D016207:Cytokines / Q000235:genetics / Q000378:metabolism / Q000494:pharmacology; D004847:Epithelial Cells / Q000166:cytology / Q000201:enzymology / Q000276:immunology*; D005260:Female; D020869:Gene Expression Profiling; D005786:Gene Expression Regulation; D006801:Humans; D018793:Interleukin-13 / Q000235:genetics / Q000378:metabolism / Q000494:pharmacology; D008297:Male; D008407:Mast Cells / Q000166:cytology / Q000201:enzymology / Q000276:immunology*; D008875:Middle Aged; D010447:Peptide Hydrolases / Q000145:classification* / Q000235:genetics / Q000378:metabolism*; D010641:Phenotype; D019089:Stem Cell Factor; D018418:Th2 Cells / Q000276:immunology*; D053802:Tryptases / Q000235:genetics / Q000378:metabolism; D055815:Young Adult
chemical_list: D016207:Cytokines; D018793:Interleukin-13; D019089:Stem Cell Factor; D010447:Peptide Hydrolases; C468648:CPA3 protein, human; D043422:Carboxypeptidases A; D053818:Chymases; D053802:Tryptases
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