OBJECTIVETo study the roles of CD4(+)CD25(+) regulatory T cells and Foxp3 mRNA in peripheral blood as well as serum total immunoglobulin E (IgE) in the pathogenesis of bronchiolitis caused by respiratory syncytial virus (RSV).

METHODSThe proportion of CD4(+)CD25(+) regulatory T cells and expression of Foxp3 mRNA in peripheral blood, and total serum IgE level were tested by flow cytometry, RT-PCR and ELISA respectively in 57 children with RSV bronchiolitis (26 atopic patients and 31 nonatopic patients). Twenty five healthy children were used as the control group.

RESULTSThe proportion of CD4(+)CD25(+) regulatory T cells in peripheral blood in children with bronchiolitis, either in the atopic (7.7+/- 1.6%)or the nonatopic group (8.8+/- 2.1%), was significantly lower than that in the control group (10.5+/- 1.6%) (P< 0.01). Foxp3 mRNA expression in peripheral blood was significantly lower in both atopic and nonatopic children with bronchiolitis than that in the control group (P< 0.01). Significantly increased total serum IgE level was noted in both atopic (241.2+/- 102.5 IU/mL) and nonatopic children (125.5+/- 63.2 IU/mL) with bronchiolitis compared with that in the control group (27.2+/- 10.5 IU/ml) (P< 0.01). There were significant differences in the proportion of CD4(+)CD25(+) regulatory T cells and Foxp3 mRNA expression in peripheral blood (P< 0.05) as well as total serum IgE level (P< 0.01) between the atopic and the nonatopic group. The proportion of CD4(+)CD25(+) regulatory T cells (r=-0.70, P< 0.01) and Foxp3 mRNA expression in peripheral blood (r=-0.79, P< 0.01) were closely negatively correlated to total serum IgE level.

CONCLUSIONSBoth the proportion of CD4(+)CD25(+) regulatory T cells and Foxp3 mRNA expression in peripheral blood were reduced, in contrast, the total serum IgE level increased in children with RSV bronchiolitis. This suggested that CD4(+)CD25(+) regulatory T cells and Foxp3 mRNA together with IgE participated in the pathogenesis of RSV bronchiolitis.