A. Shimbara et al., IL-9 and its receptor in allergic and nonallergic lung disease: Increased expression in asthma, J ALLERG CL, 105(1), 2000, pp. 108-115
Background: Bronchial asthma is a chronic inflammatory disease associated w
ith genetic components. Recently IL-9 has been reported as a candidate gene
for asthma and to be associated with bronchial hyperresponsiveness and ele
vated levels of total serum IgE.
Objective: To investigate the contribution of IL-9 to the pathogenesis of a
sthma, we examined the expression of IL-9 and its receptor (IL-9R) in bronc
hial tissue from subjects with atopic asthma (n = 10), chronic bronchitis (
n = 11), and sarcoidosis (n = 9) and from atopic (n = 7) and nonatopic (n =
10) healthy control subjects.
Methods: Bronchial biopsy specimens were examined for the presence of IL-9
and IL-9R protein and messenger RNA (mRNA) by immunocytochemistry and in si
tu hybridization, respectively. To phenotype the cells expressing IL-9 in a
sthmatic tissue, combined in situ hybridization and immunocytochemistry was
also performed.
Results: There was a highly significant difference (P < 1.001) in the expre
ssion of IL-9 mRNA in asthmatic airways (20.6 +/- 4.0 cells/mm of basement
membrane) compared with chronic bronchitis (5.6 +/- 4.4), sarcoidosis (2.5
+/- 1.8), atopic control subjects (7.7 +/- 2.2), and healthy control subjec
ts (2.7 +/- 2.3). The number of IL-9 immunoreactive cells was also greater
in asthmatic patients compared with the other groups (P < .05). Although th
e level of IL-9R mRNA expression did not differ in any of the groups (P > .
05), IL-9R immunoreactivity was significantly higher in asthmatic compared
with control subjects. Furthermore, IL-9 mRNA expression levels were also s
ignificantly correlated with FEV1 ( P < .05) and the airway responsiveness
to methacholine producing a 20% fall in PEV1 (P < .01). The cells expressin
g IL-9 mRNA in asthmatic tissue were CD3(+) lymphocytes (68%), major basic
protein(+) eosinophils (16%), and elastase(+) neutrophils (8%).
Conclusion: The results of this study demonstrate the potential of IL-9 to
be a marker for atopic asthma and furthermore suggest an important role for
this cytokine in the pathophysiologic mechanisms of this disease.