Regulatory T cell micro RNA expression changes in children with acute K awasaki disease

Summary K awasaki disease ( KD ) is a type of systemic vasculitis syndrome related to immune dysfunction. Previous studies have implicated that dysfunctional regulatory T cells ( T reg ) may be associated with the immune dysfunction in KD . In the absence of micro RNA s (mi RNA s), forkhead box protein 3 ( F oxP3) +   T reg develop but fail to maintain immune homeostasis. This study was designed to investigate the effects of mi R ‐155, mi R ‐21 and mi R ‐31 on T reg in children with KD . The proportions of CD 4 + CD 25 + F oxP3 + T reg and the mean fluorescence intensity ( MFI ) of phosphorylated‐signal transducer and activator of transcription ( pSTAT )‐5 and pSTAT‐ 3 protein in CD 4 + CD 25 + T reg were analysed by flow cytometry. The concentration of interleukin ( IL )‐6 in plasma was measured by cytometric bead array. Real‐time polymerase chain reaction was performed to detect the levels of micro RNA s and associated factors in CD 4 + CD 25 + T reg . The proportion of T reg and the mRNA levels of the associated factors [ F oxP3, glucocorticoid‐induced tumour necrosis factor‐receptor ( GITR) , cytotoxic T lymphocyte antigen (CTLA) ‐4)] were significantly lower in KD patients ( P  < 0·05). MiR ‐155 and mi R ‐21 levels were significantly down‐regulated and mi R ‐31 expression was higher in KD patients ( P  < 0·05). Plasma interleukin ( IL) ‐6 concentrations, pSTAT‐ 3 protein levels and suppressors of cytokine signalling ( SOCS)‐ 1 mRNA expression were remarkably elevated in acute KD ( P  < 0·05), while pSTAT‐ 5 protein levels were remarkably decreased in acute KD ( P  < 0·05). These findings were reversed after intravenous immunoglobulin treatment ( P  < 0·05). Our results demonstrate that F oxP3 mRNA levels were primarily affected by the mi R ‐155/ SOCS 1 and the mi R ‐31 signalling pathways. These results suggest that the decrease in F oxP3 + T reg might be associated with decreased expression of mi R ‐155, leading to aberrant SOCS 1/ STAT‐ 5 signalling and overexpression of mi R ‐31 in patients with acute KD .