Absence of Linkage Between the Interleukin-6 Promoter Gene (-174 G/C) Polymorphism and Kawasaki Disease

Abstract

Objectives. Kawasaki disease (KD), an acute vasculitis with unknown etiology, involves a complex interaction of immunoinflammatory processes, cytokine activation, and genetic factors. Gene polymorphisms of proinflammatory cytokines, such as interleukin-6 (IL-6), are associationed with cardiovascular disease. We aimed to investigate whether the IL-6 -174 promoter gene polymorphism is as a marker of susceptibility to KD. Methods. Individuals were divided into two groups: 1) KD (n=120); 2) non-KD groups (n=102). Genomic DNA was obtained from peripheral leukocytes. The IL-6 promoter gene (-174 G/C) polymorphism was amplified by polymerase chain reaction and detected after NlaIII restriction enzyme digestion. Genotypes and allelic frequencies were compared between both groups. Results. The genotype distributions and allele frequencies of the IL-6 promoter polymorphism did not differ significantly between the KD and non-KD groups. The proportions of C homozygote/heterozygote/G homozygote for IL-6 promoter in the KD group were 99.2/0.8/0%, and those in the non-KD group were 99.01/0.99/0%. The proportion of allele C/G in the KD group was 99.6/0.4%, and that in the non-KD was 99.5/0.5%. Conclusions. There is no association between KD and the IL-6 -174 G/C gene polymorphism. Differences in IL-6 genotypes and alleles are not associated with KD development. Therefore, the IL-6 -174 G/C gene polymorphism is not a genetic marker of susceptibility to KD.