Association between interleukin-18 gene polymorphism 105A/C and asthma.
BACKGROUND
IL-18 has been shown to exert anti-allergic or allergy-promoting activities, but the existence of genetic polymorphisms in the coding regions of IL-18 gene has not been demonstrated.


OBJECTIVE
The aim of this study was to investigate whether polymorphism is present in the coding regions of the IL-18 gene and, if so, to further analyse the association between polymorphism and asthma in a case-control study.


METHODS
We screened the coding regions of the IL-18 gene for polymorphisms by using PCRsingle-stranded conformation polymorphism and direct sequencing of PCR products, followed by analysis of the association between polymorphism and asthma.


RESULTS
We identified one polymorphism (105A/C) in the coding regions. The frequency of the 105A allele was significantly higher in asthmatic patients than in controls (P<0.01; odds ratio (OR)=1.83 (1.37-2.26)). Significant linkage disequilibrium was observed between the 105A/C and -137G/C polymorphisms in the 5' flanking region of the IL-18 gene (D=0.58, P<0.0001). However, in asthmatic patients the 105A allele was not associated with either total serum IgE or IL-18 levels.


CONCLUSIONS
The 105A/C polymorphism of the IL-18 gene may be associated with the pathogenesis of asthma.
Higa
S
S
Department III of Internal Medicine, Osaka University Medical School, Osaka Department of Pediatrics, Fukui Medical University School of Medicine, Fukui, Japan.
Hirano
T
T
Mayumi
M
M
Hiraoka
M
M
Ohshima
Y
Y
Nambu
M
M
Yamaguchi
E
E
Hizawa
N
N
Kondo
N
N
Matsui
E
E
Katada
Y
Y
Miyatake
A
A
Kawase
I
I
Tanaka
T
T
D000293:Adolescent; D000328:Adult; D000368:Aged; D001249:Asthma / Q000235:genetics* / Q000276:immunology; D016022:Case-Control Studies; D002648:Child; D002675:Child, Preschool; D005787:Gene Frequency; D020022:Genetic Predisposition to Disease; D005838:Genotype; D006801:Humans; D007073:Immunoglobulin E / Q000097:blood; D007223:Infant; D020382:Interleukin-18 / Q000097:blood / Q000235:genetics*; D015810:Linkage Disequilibrium / Q000276:immunology; D008875:Middle Aged; D011110:Polymorphism, Genetic; D018807:Polymorphism, Single-Stranded Conformational; D020133:Reverse Transcriptase Polymerase Chain Reaction
D020382:Interleukin-18; D007073:Immunoglobulin E