Abstract: Objective To explore the changes of histone methylation of IL-4 gene and its roles in dysfunction of Th2 cells during acute pediatric Kawasaki disease (KD).Methods Forty-two children with KD were recruited in present study, while thirty-six age-matched healthy volunteer were as controls. Flow cytometry was performed to determine the frequencies of Th2 cells and levels of IL-4, phosphorylated STAT6 (pSTAT6) and GATA3 protein. Chromatin immunoprecipitation (ChIP) and quantitative PCR were used to evaluate trimethylation of histone H3 at lysine 4 at CNS1, HSⅡ and HSVa of IL-4 gene and binding levels of GATA3 and MLL1 with loci afore-mentioned in CD4⁺ T cells. Transcription levels of IL-4, IL-5, IL-13, IL-4Rα, IL-2Rγ and SOCS5 mRNA in CD4⁺ T cells were quantitated by real-time PCR. Plasma concentrations of IL-4, IL-5 and IL-13 were analyzed by enzyme-linked immunosorbent assay.Results (1) In comparison with healthy controls, the frequencies of Th2 cells, mRNA levels and plasma concentrations of Th2 cytokines (IL-4, IL-5 and IL-13) ,and methylation levels of H3K4me3 associated with IL-4 loci (CNS1, HSⅡ and HSVa) increased significantly in patients with acute KD(P<0.05). The items mentioned afore in patients with coronary artery lesions (CAL) were found to be higher than those without coronary artery lesions (NCAL), and restored to some extent after IVIG therapy (P<0.05). (2) ChIP results showed binding abilities of GATA-3 and MLL1 proteins with IL-4 gene loci (CNS1, HSⅡ and HSVa), were up-regulated remarkably in CD4⁺ T cells from patients with acute KD (P<0.05), and down-regulated after IVIG treatment(P<0.05). There are positive correlations between binding abilities of MLL1 protein with IL-4 loci (CNS1, HSⅡ and HSVa) and transcription level of IL-4 mRNA detected during acute KD (r=0.42, 0.33, 0.39, P<0.05). In parallel, binding abilities of GATA-3 and MLL1 with the three IL-4 loci in CAL group were higher than those in NCAL group (P<0.05). ⑶ During acute phase of KD, plasma levels of IL-4 protein, and expression levels of IL-4 signaling downstream molecules (IL-4Rα, IL-2Rγ、pSTAT6 and GATA-3) and negative regulator SOCS5 increased remarkably (P<0.05), and all the items decreased after IVIG treatment (P<0.05). Furthermore, the five items aforementioned in CAL group were higher than those in NCAL group, while the last items in CAL group was lower than that in NCAL group(P<0.05).Conclusion Excessive histone methylation of H3K4me3 with IL-4 gene might be one of initiative factors resulting in aberration of Th2 cells in KD.

Key words: H3K4me3, IL-4, Immune, Kawasaki disease, MLL1