The Study Of Correlation Between The Promoter SNP Of IL-18 And Susceptivity Of Atopic Dermatitis

Atopic dermatitis (AD) is a chronic inflammatory skin disease that is strongly affected by its genetic background. They always have high levels of allergen-specific and total serum IgE. The children given diagnoses of severe AD always have asthma and allergic rhinitis. The pathogenesis of AD is not clear yet. It results from a complex interplay between strong genetic and environmental factors. In previous studies, many predisposing genes of AD have been found. Such as 13q12,3q21,1q21 et al. The conclusions are not coincidenct yet. It may be concerned with the diagnoses principle, penetrance and study strategy of AD. The frequency of IL-18 gene distribution is different with race and region. Therefore, it is necessary to research the predisposing genes of AD in Chongqing.IL-18 is a multieffect cytokine. It has played an important role in immune response. It can regulate TH1 and TH2 response, inhibite or upregulate IgE synthesis. Learning more about the relationship between the IL-18 gene and AD is necessary to elucidate the pathogenesis of AD.Object: 1. To study the correlation between the total serum IgE and AD. 2. To detect the possible association between SNPs -137[G/C], -607[C/A] in promoter region 1 of exon 2 of IL-18 and AD patients in Chongqing. 3. To study the association of SNP of IL-18 promotor and the serum level of IL-18 of AD patients.Methods: The study was conducted in two different groups: patients with AD (the case group, n=82) and healthy people (the control group, n=100). The case group was diagnosed on the basis of the diagnostic criteria of Hanifin and Rajka. The total serum IgE levels were measured by Enzyme linked immunosorbent assay. To detect the serum IL-18 level and to observe the frequency of polymorphic alleles -137[G/C] and -607[C/A] in promoter 1 of the IL-18 gene in the two groups through the methods of Enzyme linked immunosorbent assay and polymerase chain reaction(PCR)- sequence specific primers( SSP) .Results: 1. 63 out of 82 AD patents have elevated total IgE (76.82%). The total IgE level is consistent with the severity of skin lesions. 2. The mutation at -137[G/C] in promoter 1 had three genotypes: G/G, G/C, C/C. There was statistical difference of the genotype between the case group and the control group. The probability of G/C genotype and C allele was more than the other genotype and G allele.(χ2=4.536,P=0.033). In the case group, the probability of C allele of the group A(SCORAD≥50) was significantly higher than group B(SCORAD20—50) and group C(SCORAD≤20) (χ2=3.926 , P=0.048). 3. There was no statistical difference of the allele frequency of -607[C/A] among the groupA, B and C in case group. ( P>0.05). 4. The odds ratio (OR) of -137C allele is 1.76, and OR of -137[G/C] genotype is 2.33. We can conclude that -137[G/C] is one of the predisposing genes of AD. 5. The average serum IL-18 level of the case group(239.14±153.51pg/ml) is significantly higher than that of the control group(65.75±16.16 pg/ml). There was statistical difference between the two groups. The -137C allele is consistent with the serum IL-18 level. 6. There was statistical difference of the serum IL-18 level between the -137G/G genotype of the case group(203.61±65.98 pg/ml) and the control group(64.50±14.98 pg/ml). There was statistical difference of the serum IL-18 level between the -137G/C genotype of the case group(271.44±198.63 pg/ml) and the control group too(69.09±20.15 pg/ml). There was no statistical difference between the serum IL-18 level of -137G/C and -137G/G genotype of the case group.Conclusion: 1. The children with AD have a high level of total serum IgE, and it is consistent with the severity of skin lesions. 2. The -137[G/C] genotype of IL-18 is a predisposing gene of AD in Chongqing. 3. The children with AD have a high level of serum IL-18, and there was statistical difference of the serum IL-18 level between the -137G/G genotype of the case group and the control group. The serum IL-18 level of -137G/C genotype of the case group was significantly higher than that of the control group.