Sputum and bronchial submucosal IL-13 expression in asthma and eosinophilic bronchitis.
BACKGROUND
Nonasthmatic eosinophilic bronchitis is a condition characterized by the presence of eosinophilic airway inflammation in the absence of airflow obstruction or airway hyperresponsiveness. In asthma, the T H 2-type cytokine IL-13 has been implicated in the development of airway inflammation and hyperresponsiveness. Whether the expression of IL-13 is different between these 2 conditions is unknown.


OBJECTIVE
We sought to investigate whether IL-13 expression is increased in asthma compared with eosinophilic bronchitis.


METHODS
Sputum samples from subjects with mild asthma (n = 30) and eosinophilic bronchitis (n = 15) and normal controls (n = 16) were dialyzed, and IL-13 concentration was measured by ELISA. In a subgroup of these patients, IL-13 protein expression in bronchial biopsies was assessed by immunohistochemistry.


RESULTS
The concentration of sputum IL-13 was higher in patients with mild asthma than in normal controls ( P = .03) and in patients with eosinophilic bronchitis ( P = .03). The median (interquartile range) number of IL-13 + cells/mm 2 submucosa was significantly higher in asthma 4 (8) than eosinophilic bronchitis 1.7 (1.9) and normal controls 0.5 (1.1; P = .004). Eighty-three percent of the cells expressing IL-13 in the submucosa were eosinophils, and 8% were mast cells. The median (interquartile range) proportion of eosinophils that expressed IL-13 was higher in the subjects with asthma, 16 (10)%, than those with eosinophilic bronchitis, 7 (3)% ( P = .02).


CONCLUSIONS
The increased expression of IL-13 in asthma compared with eosinophilic bronchitis supports the concept that IL-13 may play a critical role in the pathophysiology of asthma.
Berry
Mike A
MA
Institute for Lung Health, University Hospitals of Leicester, Groby Road, Leicester LE3 9QP, UK.
Parker
Deborah
D
Neale
Natalie
N
Woodman
Lucy
L
Morgan
Angela
A
Monk
Phillip
P
Bradding
Peter
P
Wardlaw
Andrew J
AJ
Pavord
Ian D
ID
Brightling
Christopher E
CE
D000328:Adult; D000368:Aged; D001249:Asthma / Q000276:immunology*; D001980:Bronchi / Q000737:chemistry*; D001991:Bronchitis / Q000276:immunology*; D004797:Enzyme-Linked Immunosorbent Assay; D004802:Eosinophilia / Q000276:immunology*; D005260:Female; D006801:Humans; D018793:Interleukin-13 / Q000032:analysis*; D008297:Male; D008875:Middle Aged; D020545:Respiratory Mucosa / Q000737:chemistry; D013183:Sputum / Q000737:chemistry*
D018793:Interleukin-13