Increased sputum and bronchial biopsy IL-13 expression in severe asthma.
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.
Saha
Shironjit K
SK
Institute for Lung Health, Clinical Sciences Wing, University Hospitals of Leicester, Leicester, United Kingdom.
Berry
Mike A
MA
Parker
Deborah
D
Siddiqui
Salman
S
Morgan
Angela
A
May
Richard
R
Monk
Phillip
P
Bradding
Peter
P
Wardlaw
Andrew J
AJ
Pavord
Ian D
ID
Brightling
Christopher E
CE
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
D018793:Interleukin-13