title: Increased sputum and bronchial biopsy IL-13 expression in severe asthma.
abstract: BACKGROUND
  The importance of IL-13 in the asthma paradigm is supported by increased expression in human subjects, particularly in patients with mild-to-moderate asthma. However, the role of IL-13 in severe asthma needs to be further defined.
  
  
  OBJECTIVE
  We sought to assess IL-13 expression in sputum and bronchial biopsy specimens from subjects with mild-to-severe asthma.
  
  
  METHODS
  Sputum IL-13 concentrations were measured in 32 control subjects, 34 subjects with mild asthma, 21 subjects with moderate asthma, and 26 subjects with severe asthma. Enumeration of mast cells, eosinophils, and IL-13+ cells in the bronchial submucosa and airway smooth muscle (ASM) bundle was performed in 7 control subjects, 14 subjects with mild asthma, 7 subjects with moderate asthma, and 7 subjects with severe asthma.
  
  
  RESULTS
  The proportion of subjects with measurable IL-13 in the sputum was increased in the mild asthma group (15/34) and severe asthma group (10/26) compared with that seen in the control group (4/32; P = .004). IL-13+ cells were increased within the submucosa in all asthma severity groups compared with control subjects (P = .006). The number of IL-13+ cells were increased within the ASM bundle in the severe asthma group compared with that seen in the other groups (P < .05). Asthma control questionnaire scores positively correlated with sputum IL-13 concentrations (R(s) = 0.35, P = .04) and mast cells in the ASM bundle (R(s) = 0.7, P = .007). IL-13+ cells within the submucosa and ASM correlated with sputum eosinophilia (R(s) = 0.4, P < or = .05).
  
  
  CONCLUSIONS
  IL-13 overexpression in sputum and bronchial biopsy specimens is a feature of severe asthma.
authors.affiliation: Institute for Lung Health, Clinical Sciences Wing, University Hospitals of Leicester, Leicester, United Kingdom.
authors.forename: Shironjit K
authors.initials: SK
authors.lastname: Saha
authors.forename: Mike A
authors.initials: MA
authors.lastname: Berry
authors.forename: Deborah
authors.initials: D
authors.lastname: Parker
authors.forename: Salman
authors.initials: S
authors.lastname: Siddiqui
authors.forename: Angela
authors.initials: A
authors.lastname: Morgan
authors.forename: Richard
authors.initials: R
authors.lastname: May
authors.forename: Phillip
authors.initials: P
authors.lastname: Monk
authors.forename: Peter
authors.initials: P
authors.lastname: Bradding
authors.forename: Andrew J
authors.initials: AJ
authors.lastname: Wardlaw
authors.forename: Ian D
authors.initials: ID
authors.lastname: Pavord
authors.forename: Christopher E
authors.initials: CE
authors.lastname: Brightling
mesh_terms: D001249:Asthma / Q000276:immunology / Q000378:metabolism* / Q000503:physiopathology*; D001706:Biopsy; D001980:Bronchi / Q000166:cytology / Q000276:immunology* / Q000378:metabolism; D003430:Cross-Sectional Studies; D004797:Enzyme-Linked Immunosorbent Assay; D005260:Female; D006801:Humans; D018793:Interleukin-13 / Q000096:biosynthesis*; D008297:Male; D008407:Mast Cells / Q000276:immunology; D008875:Middle Aged; D009130:Muscle, Smooth / Q000276:immunology; D012129:Respiratory Function Tests; D013183:Sputum / Q000737:chemistry* / Q000276:immunology
chemical_list: D018793:Interleukin-13