Interleukin 6 gene promoter polymorphism is not associated with Kawasaki disease

We examined the IL-6 gene promoter and detected several interesting promoter polymorphisms: GGGCTG insertion at +162 bp and G deletion at +168 bp positions (M1), A to G substitution at -594 bp (M2) of the reported IL-6 promoter sequence. Other rare variations were also observed at several positions: -583 bp (T insertion), -507 bp (C insertion), -71 bp (T deletion), +17 bp (C insertion), and +121 bp (GC insertion). Although Kawasaki disease (KD) patients demonstrate a drastic increase in serum interleukin-6 (IL-6) during the acute phase that parallels the duration of fever, there were no significant differences in the nucleotide sequence between the KD patients and normal control group. By transient transfection with IL-6 gene promoter-luciferase fusion plasmids into CV-1 cells, we tested the functional significances of the polymorphisms. Mutations at +162 bp, +168 bp and -594 bp significantly decreased luciferase expression (P < 0.05), suggesting the promoter elements flanking the mutated nucleotides are important in transcriptional activation.